Check Engine light on since 2013?

Hello, so for this year being its age, the service information wiring diagrams are not very helpful, but with all these sensors alone setting codes, the Intake air temp sensor (IAT), Coolant temp sensor (ECT), and the Barometric pressure sensor most likely all share the same 5 volt reference voltage regulator inside the ECM. When it comes to thermistor's which is what the IAT sensor and ECT sensor are, to check the 5-volt feed, the sensor needs to be unplugged to check for a full 5-volt feed. Key On, Engine Off, one of the two wires to the sensor should read 5-volts, if for some reason that 5-volt feed is shorted out, whether its inside the ECM or another sensor causing it, it will cause those sensors not to read as an input to the ECM.

Service info does provide the pinout for the ECM connector which, after you check at the sensors for its 5-volt, if something doesn't look right, you would check it at the ECM. It sounds like the "new" ECM you installed, being a remanufactured computer, might have come with problems, many rebuilds do. But this is a very basic setup except that you can't get the best live engine data on a scan tool being that this is an OBD1 system, newer systems from 1996 and newer are all OBD2 with advanced scan tool options.
I would start by checking the IAT sensor unplugged, if 5 volts is there, plug it back in and check the ECT unplugged, I say thing because if either the IAT is shorted out the 5 volts, or the ECT is shorted out, you won't know when checking the next sensor if the previous sensor is still unplugged during testing, if that makes sense.
I see in the ECM pinout diagram there is only 1 sensor 5volt reference feed for them all, so that's something to check.

I would also do a voltage drop test on the ECM grounds. If this computer has a temperature related issue, such as a cracked solder joint inside, you will end up with thermal type issues like this. And unfortunately checking at the ECM connector will not tell you if there's a cracked solder joint on the circuit board.
But in some cases, a bad ECM ground can cause the 5volt reference to rise to a higher voltage, bad grounds can cause all kinds of very difficult issues, especially when they are internal to the ECM itself.
But I will post the ECM pinout for its connector so you can check the voltage readings at it if necessary.

To do a voltage drop test, for example you are measuring from Positive to Positive, so if checking for voltage drop from the Battery + to the ECM B+ feed, you would have a meter set to DC volts and check from Battery + (positive) to the wire that feeds the ECM B+ and with the vehicle running it should be as close to 0volts as possible, there will be a little bit but it shouldn't be over 0.5volt at its extreme max, so when the vehicle is hot and some electrical loads are on such as headlights, etc.


https://www.2carpros.com/articles/how-to-use-a-voltmeter

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

https://www.2carpros.com/articles/everything-goes-dead-when-engine-is-cranked

These are the ECM connector pinouts, there are additional voltage values for each pin I will post next, since this doesn't seem to list all pins.

These are the voltage values you should read with the key on, and then engine running.

This is a simplified voltage drop testing diagram, excuse my artwork.

Do you have the diagrams to show me accurately where the intake air temperature sensor is engine coolant temperature sensor and the barometric pressure sensor and if there's an engine position sensor, where it is located. I know those are basic knowledge for someone like you, but that's not the case with me.

The wiring diagrams for this year are very difficult to read and were hidden on the transmission wiring diagrams, but the Intake Air Temp sensor and the Barometric Pressure sensor are built into the Mass Air Flow sensor which is part of the air filter housing, so you should see a 5 or 6 wire connector going to it.
Sorry for the delay, hopefully these diagrams are easily understood, if you have any questions on testing, just ask, It sounds like a part of the Mass air flow sensor (volume air flow sensor) may have stopped working, or there may be some corroded connectors in between the sensors and the ECM (engine computer). Since it's only these 4 sensors setting codes and not others. There are other sensors that work off the 5volt reference that appear to not be setting any codes, such as the Mass air flow sensor, but other sensors built into that one component are setting codes, so it can be tricky.
I would start by verifying the 5volt feeds wires to the sensor in the air box, at its connector. I've tried to add as many details as possible to the wiring diagrams, but I know this testing can be difficult if you're not familiar with it.
When checking for any of these 5volt feeds, use Battery negative as your meter ground (black lead) and the red lead for reading the voltage levels with the Key On, engine off to begin with. I will try to locate the Coolant temperature sensor as well.

https://www.2carpros.com/articles/how-to-use-a-voltmeter

Here is the location for the coolant temperature sensor, there looks to be another temperature switch by it that is probably just a one wire temperature switch and not the sensor setting the code.

Idle speed motor position sensor pin voltage readings:
1 has no wire - you said it might be a case ground.
2 (GR wire) 5.0 volts.
3 (GB wire) 0 volts.
4 (G wire) 11.3 volts.
5 (Br wire) 0 volts.
6 (GR wire) 5.0 volts.
Pins 4&5 might be a problem as you said pin 4 should read either 0 or 5 volts and pin 5 should be the voltage to the ECM (computer).

DROP TEST RESULTS: .7 volts

ECM voltage readings- temp 83° 250' pressure altitude key on:
Pin 8 - volts 1.1 IATS
Pin 16 - volts 2.3 barometric pressure sensor
Pin 20 - volts 1.1 ECTS
Pin 19 - volts .3 throttle at idle volts 2.9 throttle full open - throttle position sensor.

Engine running voltage readings:
Pin 8 - volts 1.7
Pin 16 - volts 3.3
Pin 20 - volts .4
Pin 19 - volts .5
Pin 10 - volts 2.5 idle and at 2000rpm was same - VAFS volume air flow sensor.

The air intake temperature sensor, barometric pressure sensor and engine coolant temperature sensor all seem to be off with the key on engine not running per the parameters listed with the pinout diagrams.

I'm still having trouble understanding all the variations in the components involved in the engine, electronics and components or accessories of the car, so please be patient and allow errors on my part.

I read 9.3 volts on the 1 wire sensor beside the 2 wire engine coolant temperature sensor because I was curious what it was and it had volts.

Thank you very much for helping!

I sent these voltage readings from the six pin connector at the MASS AIR FLOW SENSOR a few days ago but I didn't see the post on your site:
IATS Pin 1 (GL wire) 4.5 volts.
Pin 2 (Red wire) 12.5 or battery volts.
Pin 3 (GR wire) 5.0 volts.
Pin 4 (GB wire) 0 volts.
Pin 5 (GY wire) 0 volts.
Pin 6 (GY wire) 3.9 volts -barometric pressure sensor.

Engine coolant temperature sensor with two wires:
Yellow with green stripe - 3.9 volts
Volts 0 (GB wire).

I didn't see any ground connectors to the car that had corrosion in my opinion.

Thank you for helping.

Hello, I'm sorry for the delay, I am in North Carolina just east of where the storm hit and we're sending supplies to people we know in Asheville, I do apologize for not getting back to you sooner.
It does look like some of those readings are off, I will have to pull up the file on your vehicle again and review the diagram again, but with thermistor components such as the IAT and ECT, the ECM sends out 5-volts to the sensor and the ECM monitors that 5volts internally for any change in voltage. And because the thermistor is basically a resistor that changes resistance with temperature fluctuations, higher or lower temperatures will cause the sensor to vary the voltage the ECM is seeing on the monitoring circuit through a resistor. The resistor helps also if the 5volt ref happens to be shorted to ground. It's a protection device. Let me look over your testing results really quick.

Okay, so on the idle speed motor, pin 5 is the motor's position signal wire, it should not be just 0 volts, you notice how it is in between pin 3 and pin 6, here's some resistance checks to do on the position sensor. You're missing the motor's position signal to the ECM.

This is additional testing for Code 13, I'm going to post these, because I'm seeing some service info that varies a lot.

This is for Code 15, the ISC motor position sensor's resistance value is actually only 4000-6000 Ohms.

This is Code 21 ECT.

But Code 23 in service info is not listed as Baro sensor, it is stating a camshaft position fault. The Barometric pressure sensor fault is listed as Code 25 (diagram 3). I don't know if that was a scan tool reading the code incorrectly, the camshaft and crankshaft position sensors are inside the Distributor on this vehicle, and if they were not functioning, you would have a crank no start condition.

My ohms selection of Rx1k and Rx10 reads exactly the same, so I am giving these values as if it is R1k.
Idle speed motor position sensor:
PIN 2 GR = 0
PIN 3 GB = 0 tested to battery
PIN 4 G = 2000
PIN 5 Br =9000
PIN 6 GR = 0

Volume air flow sensor:
The PIN numbers and the color of wires do not match up per the A35 connector on the diagram you attached.
GL = 800 ohms
R wire = 1200
GR = 0
GB = 0 to the battery gnd.
GY = 9000
GO = 1600

Coolant temperature sensor:
YG wire= 1600
GB = 0 to battery

Notice the GO and YG wires have the same ohms and they both had 3.9 volts, and I think they both are supposed to have 4.5 to 4.9 per the maintenance charts you attached and the charts say to repair the harness.

I installed a new distributor and it performed just like the one that I had in there, so I put my old one back in and I'm going to send the new one back because I don't need a bunch of spare parts if I never get this car to run right. I will rule out the cam and crankshaft sensors because of that distributor and I also checked the volts at the engine control module and they seemed to meet the variables on the chart.

I'm not surprised if some of the wire colors are not correct, this is very old service information. I'm going to post this info first, but I'm looking over your readings you took at the ECM again, it states 83f degrees out, but the IAT sensor is at 1.1v and the ECT is the same These are Key On engine Off readings I assume,

But the Pin 19 is the Throttle Position sensor that's the incorrect sensor, we need ECM Pin 17 that is the Idle Speed motor position. If Pin 17 at the ECM is reading 0volts like it is at the idle speed motor, that's why the code is setting.

some of these wire colors will fade over the years and it can be difficult to tell what color they are. So for A-35 we will have to go with wire/pin location in the connector.
It might also be that, when disconnected they are showing the connector face (so the wiring harness side of the sensor's circuit), looking at the female pins of the connector.

While checking the Idle Speed Control motor position sensor (diagram 1 below) you didn'tt have 4000-6000 Ohms (4k-6k) across pins 2 and 3?
We just need to know if the sensor is open circuit inside (diagram 2). I think you were testing the harness side of the circuit, when unplugging it, check the male pins inside the sensor side, not the harness side.

we need to check each sensor that is setting a code for an open circuit internally first, If that reads ok, then we move on.
So its the same with the coolant temperature sensor, unplug the two wire connector, move it aside and measure the sensors male pins. Sorry I know these wiring diagrams are not the best by any means.

Thats why in the 3rd diagram when checking pin 3 you had 0 ohms because its the sensors ground wire. But since these diagrams are so old, we would load test wires these days and only use continuity testing to see if there was a short to ground...
The low voltage is a concern though, diagram 4 and 5 are for the IAT 5v reference at the sensor connector(unplugged) and then the ECM connector(plugged in still) back probed.

Those low voltages will cause incorrect readings, and starting issues if the ECT has low voltage because the coolant temp sensor is the main sensor the ECM looks at during a cold start.

This is the code setting criteria for Code 13 IAT. With the engine running, readings at ECM pin 8 at 1.7volts looks normal, or within range around 104f degrees, which is okay.

The next is Code 21 ECT, running at 0.4volts is around 180f degrees, which looks normal too.,
So, this might be an intermittent issue with this ECM, obviously you're getting some lower-than-normal 5v reference readings. But Pin 17 needs to be checked to verify this code 15 ISC motor position,
But I would recheck the pin 8 and pin 20 with both the IAT and ECT sensors unplugged at the same time and see if the full 5volts comes back,

The Code 23, we will have to check last, because it's listed as Cam sensor,
But you can see the code setting criteria in the diagrams 1 and 2 below, it's possible the ECM circuit board may be having an issue either when hot or cold. And that's when these codes are setting, these older ECMs are also pretty easy to repair if this is a soldering or corrosion issue on the circuit board. I've repaired them in the past, due to broken solder traces and such.

The 11.4volts on Pin 4 of the ISC motor position sensor is incorrect unless service info is wrong on what voltage is supposed to be on that wire, because it's the position sensor setting the code, and we need to know if that is open circuit or not inside the sensor, if Pin 5 was checked with the sensor unplugged you would read nothing, we need to resistance value on pins 2 and 3. I'll post that again (diagram 5).

You are correct; all of my readings were from the harness or the female side (sorry) it never occurred to me to check the sensor. I assume the redo readings for pin 8 and 20 in the engine control module with the idle speed control motor position connector and the engine coolant temperature connectors disconnected are with the key on but not idling the engine - I know that sounds like a stupid question, but you deserve a lot better than you're getting from me because if it can be screwed up - I'll screw it up.
I do have on my code list from 2013 the camshaft sensor and the mass air flow sensor but they didn't have a number written by them, so there was probably some confusion. This reading was done in 2013 and there were several people helping me or doing it for me actually. I tried to have the codes read again last week as they do have the correct connection, but the device said something like failure to communicate or connect.
I did not tell you that the car turns off when it gets hot because a mechanic told me that the problem was caused by low coolant, but I don't know how that turns the car off and makes it not start until it cools off for an hour and the temperature needle never goes up on the instrument panel. I also had driven the car until the instrument panel needle was in the red (hot and it never shut down) one summer trying to get to a water hose after the belt broke that turned off the water pump and some other things. I noticed the new replacement distributor would not shut the car down like my original distributor when it got hot, but the new replacement distributor wouldn't start when it was hot (might be a battery with a temperature problem or short), and the original distributor was the one that shut down when it gets hot and now that I put the original distributor back in - the car shut down again today when it got hot. But the original distributor will still start once it cools down - I think it takes a little over an hour for it to cool down and start again. There is damage to the coating or framing of the plug connection of both the six pin distributor connection and the six pin idle speed control motor position sensor connector. It might take me a few days to try to make sense of what I have to do, but I will be working on it.

Well, don't be too hard on yourself, the crank sensor and cam sensor are inside the Distributor, along with the ignition coil and a power transistor that triggers the coil on and off. A common symptom of a bad crank or cam sensor is a hot or cold stalling issue, more on the hot side like you are experiencing, when the sensor gets hot, it expands and if there is a wire (winding) in the crank or cam sensor that is touching when it's cold, it will open up when hot, and there's your stalling issue. It will cool down and start to function again.
I would clear the codes out completely and see what ones come back now, since it's been so many years.

As for checking Pin 8 and 20 at the ECM, Pin 8 is the Intake Air Temp sensor, Pin 20 is the ECTemp sensor. I would unplug them both at the sensor, then key On, engine Off, see if the full 5 volts comes back on both wires,

There might be more than one 5-volt regulator inside the ECM, it's unlikely on an old computer like this, but who knows.

Now depending on how bad the damage is to the connector of the idle motor sensor, if there are wires that are shorting together, meaning the pins inside the connector are touching in any way, that might be the issue for all these problems, the damaged connector is most likely going to be the cause of the Code 15.

I'll explain; if this ECM has just one 5-volt supply internally that it uses for all the sensors in the vehicle, and if the idle motor position sensor connector is shorting out the 5-volts to ground or to another wire that's pulling it low, such as the lower voltage you were reading, that is going to affect multiple sensors, and if it is an intermittent issue where the wire is shorting out, then it's not, then it is, you can see the turmoil that will cause.

Pin 23 and 13 of the ECM are supposed to be a 5volt reference for the sensors, you can see it in the diagram that goes to the idle motor position sensor.
It might not be the Distributor that's getting hot and causing the stall though, if the new one has the same symptoms, it might be the ECM getting hot and shutting down the vehicle.

When it shuts down when hot, turn the key On and see if the Check Engine light comes on for a few seconds, if it doesn't that indicates the ECM is probably not powering up, also check the 5volt Ref when its stalls out hot, Pin 23. I'll bet it will be missing or low voltage.

A bad ECM is difficult to diagnose. Sorry, this is all so complicated, it's because we are dealing with multiple codes, but erase them if possible and see what comes back, if you don't have a scan tool you can ***disconnect the battery for at least 10 seconds should clear the codes.

Reading codes on this system you will need a scan tool with an OBD1 adapter to it. (3rd diagram shows how they want you to read codes without a scan tool which requires an Analog multimeter, which I don't even know where you would get one that old anymore.)

Can you take a picture of the connector for the idle motor sensor so I can see the damage to it?

I will take a picture of the two damaged connectors tomorrow and send them to you.
The new distributor never shut down, so I bet the original distributor is doing what you said when it gets hot and expanding causing a disconnection - I actually don't understand it or can't visualize it, but I believe it.

Below are the ohms readings of the male contact or pin that is part of the idle speed control motor sensor that the harness connects to:
PIN 2 GR 4500
PIN 3 gnd used to do readings
PIN 4 G 0 ohms
PIN 5 Br 450
PIN 6 GR 4500

Below are the ohms readings from the volume air flow sensor male pins identified by the wires color from the harness because the pins don't match what the diagram A35 shows: I am showing two readings because they were not consistent.
GL 3200 / 2400
Red 2300 / 1600
GR 2300 / 1600
GB gnd used for all readings
GY 4100 / 2600
GO 1900 / 900

ECT ohms reading:
YG 900

PIN 17 in ECM with key on but engine not running was .3 volts.
I had the engine coolant temperature harness unplugged and the volume air flow sensor harness unplugged during that check. I'm not sure if I was supposed to run an ohm's check from PIN 17 to PIN 5, but they are both a brown wire (Br) and it seemed like one of those diagrams did a check like that.

I will try to check ECM pins 8 (IATS) and 20 (ECTS) again as they were both 1.1 volts last time I checked them. I will also try to check ECM pins 13 and 23 for the 5 volt reference.

The six wires in the harness going to the distributor are difficult to identify - seem like 4 of them are a gray or blue gray color and then there's one green with the yellow stripe and one orange with the yellow stripe. I might try to find one or two of them at the engine control module to see the signal.

The crank and cam sensors inside the Distributor are pick up (variable reluctance) type of sensors, so they are a coil of wire and when a part of a trigger wheel passes by the pick up for the sensor it sends a signal, now it could also be the transistor getting hot inside and failing as well, this is a diagram of the Distributor, the Ignition Power Transistor is a solid state device, which is inside an ignition module inside the Distributor, but long story, short, it can act with the same hot/cold fault.

***Now onto the idle motor sensor, the resistance reading is within spec, so its not open circuit, 4.5k Ohms from pin 2 to pin 3, then also pin 6 to pin 3 is correct. I would say on this, the connector needs to be repaired or replaced. ***I would do this first and see if it resolves the other codes.

Pin 5 being your signal wire, 450 ohms is most likely the position of the motor at this time, you are correct that Pin 5 is the same wire that goes to pin 17 of the ECM, you can unplug the ECM and the idle motor and check the resistance from pin 5 to pin 17, you should have roughly 5 ohms or less since you are just checking from one end of the wire to the other end. Diagram 2 below is the voltage reading you should have on pin 17 with everything plugged in and engine idling.

Did you take the new Distributor back out? Sorry we are just testing so many components here Im trying to keep track of where we are at.

The reason I wanted you to check for 5volts on pin 8 and 20 was to make sure that either the IAT or ECT sensors were not shorted out and effecting the other sensors, if one is shorted out and pulling down the 5volts, it can cause other sensors to set codes as well.
This is the Air Volume sensor youre dealing with, its a pretty complex sensor for a 1993. Its also about $120 from rockauto. Just resistance readings jumping around like that can be caused by potential solder joint issues inside, since you had steady readings on the other sensor I dont think its a multimeter issue, but resistance will jump around like that when the circuit being tested doesnt have a good complete circuit,

whats difficult about this sensor is with service info they want you to see what a scan tool is reading from the sensor compared to the actual temperature. For code 13 they have you check scan tool data temperature reading, then check the ground for the sensor and then just the 5volt ref, and thats it, (diagram 5). So youre previous check of the unplugged 5volt ref that was low, is really our only clue as to what might be setting the code.

You can do the same check on the wire from ECM pin 8 to IAT pin 6, except with the colors being incorrect, service info doesnt help us much, the only thing you can really do is see if ECM pin 8 has a resistance reading to one of the 6 wires of the connector.

The Code 21 ECT info is on diagram 7.
I feel terrible to be overloading you with so much info at once here as well, and if we are dealing with a low 5volt reference causing these codes, that opens up a whole other can of worms, But do your best, ECM pin 23 should remain at 5v as well.
Sorry again for the long posts, but do the idle motor connector repair first,

Key on and engine off with VAFS harness disconnected, ISC MOTOR POSITION SENSOR harness disconnected and ECT harness disconnected readings at ECM:
PIN 13 - 5 volts
PIN 23 - 5 volts
PIN 8 - 3.9 volts to IAT sensor
PIN 20 - 3.9 volts to ECT sensor
Last time I checked PIN 8 and PIN 20 with the harnesses connected they were the same at 1.1 volts with key on engine off and now they're the same at 3.9 volts with the key on and the harnesses disconnected and these two pins are right next to each other at the ECM. Could these two (pins 8 and 20) be shorted together between the engine control module and the sensors.
I attached photos of the idle speed control motor position sensor harness connector for you to evaluate the damage, but I doubt if it's the problem because these codes were there in 2013 and I doubt if the harness had much if any damage in 2013.
I was going to try to read the codes again with the ohms reading, but there's four wires in the diagnostic connector and I couldn't find where the diagram indicate which wire to connect to which lead from the multimeter. I believe only one of the wires is dark and the other three are either creamy or white color.

I believe I am the cause of the car shutting off when it gets hot because I traded a battery that I unsuccessfully tried to recondition (I'm not even sure reconditioning a battery is possible) for a used battery that would start the car - only since that battery swap has this problem of the car shutting down been in existence. Batteries go bad over time and they must be charged by a charger or used and charged by the alternator or they go bad faster, and this car only drives about a hundred miles every 6 months - keeping a new battery in it, it is kind of like the mechanic shop that replaced a working fuel pump in the car to get the check engine light to go out and charging me $55 for the inaccurate diagnostics and over $200 for the pump and labor - I understand all of that was my fault not their fault.

The first thing I noticed when the car shuts down from heat is all the lights in the instrument warning panel come on and the engine still cranks while it's hot (that might rule out the ECM since the check engine light is on immediately and the car cranks with all the instrument panel warning lights on), but it will not start for about an hour and that might vary with atmospheric temperature. Some distributors may react differently to battery hot and over and under voltage issues caused by batteries, and that maybe why the one distributor wouldn't shut down the car, but it wouldn't start when the battery got hot and the other distributor shuts down the car. I feel bad about all the problems that are directly or indirectly my fault and causing you diagnostic complications.

Oh dont feel bad, you wouldnt believe some of the messes we get into here, I have spent months with certain people trying to explain even the simplest things to them, so youre all good, no worries.

So as for your question on the two sensors possibly having their wiring shorted together, yes that can absolutely happen, to check that, unplug both sensors, and unplug the ECM connector they go to and just check pin 20 and pin 8 at the ECM connector for continuity between the two, there shouldnt be any reading between the two of them, with both ends
of the circuit open while unplugged they should read OL on the meter.

Another test you can do is with them both still unplugged, check for continuity to ground (Battery Negative) on either wire, there should also be no reading from that test. If you read anything, the wires can be shorted to ground somewhere, its common to find wires melted together at location where they might be touching the exhaust or a contact location where they have been rubbing on metal over the years and they short out that way.

A corroded connector can also short circuits together, if water or some other liquid has gotten into something like a bulk connector, in that case you will find a bunch of green or white crusty corrosion inside the pins of the connector. Even a pin hole of a wire can corrode inside, and the corrosion can just grow inside the wire insulation breaking the copper strains, those are difficult to find because you cant actually see the corrosion.
So following the wiring in the harness from a sensor will sometimes lead you to a location where the wiring is just a complete mess.

From your readings it sounds like Pin 13 & 23 are a different voltage regulator inside the ECM and pin 8 and 20 share a different 5volt regulator, or most likely you would be reading the same 3.8 volts on 8 and 20 as well.

The best thing for you to do if the vehicle is not going to be driven for a while is unhook the negative battery cable, that will prevent it from draining as fast.
When a battery goes bad, it can be the result of either being tightened down too much, in which the cells inside the battery actually get crushed and shorted together, many people tighten the battery hold down too much, you can tell when you see a battery that has the top squished down and the sides are bulging out. That happens a lot when places like auto parts stores replace the battery for a customer and over tighten it.
And batteries also just age, and become sulfated inside which also shorts out the cells inside, there are 6 cells in a 12v lead acid battery, 2volts per cell, so when 2 cells get shorted together, the battery can no longer be fully charged or hold a charge.
A bad battery will also eventually take the Alternator out, due to it being overworked trying to charge a bad battery.

With that said, the 3.8 volts is an issue, if you do not find a wiring problem, we will have to check the ECM powers and grounds for any voltage drop while the vehicle is running with some electrical loads on.

The ISC motor sensor gets its 5volts from pins 13 and 23, and the resistance reading of the sensor was within spec, so these are the voltage values you should expect on ECM pin 17 while its running, I know I posted this already, but something else to recheck since we seem to be getting to the bottom of seeing what the causes of some of these codes are. It looks like there are just possibly multiple problems which is not surprising.

Look for rodents nests too, vehicles not driven much seem to always have more rodent damage to wiring harnesses. Ive seen so many those. Especially under the passenger side dash where the blower motor is, they love to make nests in those areas, and they eat the insulation on the wires because it contains a chemical they like the taste of. Pretty gross.

There is some white stuff that was like a cream when I first saw it inside of a connector that connects two wires that go to the bottom of the radiator reservoir or overflow. I will try to clean that connector if possible. I should have asked you because I was wondering if that was supposed to be in there as some kind of lubricant. Would it be okay to just disconnect that possible corroded connection and see if it is causing problems after I run the checks on PIN 17. I do or did have a rodent problem because there were peanut hulls near my volume air flow air inlet and it looked like it tried to start a nest inside of the air filter container but the air filter blocked the rodent from going any further - where the sensors are. I tied the guard to that air inlet up against it so that the rodent couldn't get in behind it like it was previously.

Usually corrosion inside connectors will turn into a crusty type of corrosion that is flaky and is what we call the green crustys, but it can be white in color too, what your describing sounds more like someone put dielectric grease into the connector to prevent moisture from getting in, what most people dont understand about dielectric grease is that it does not conduct electricity, they seem to think it does, but its safe to use because it wont corroded electrical connectors. You can get a spray can of electrical connector cleaner at autozone or other auto part stores, thats safe to spray right into connector pins and it will clean and then dry not leaving any residue behind. So you may want to check any other bulk connectors in the engine compartment for corrosion inside, this low voltage issue might be a result of a main power feed to the ECM not suppling full voltage or there could be resistance in a circuit, Ill check on how many powers and grounds there are to the ECM as well.

Those two wires going to the reservoir may be for a float or something that triggers a low coolant warning light.
For the rodent damage, they will eat right through an air filter too, what guard are you referring to that you tied up to the air flow sensor?

I will look and see if I can find the two wires to the coolant res, you can unplug it and just see if the low coolant light comes on, I dont think it will have any effect on starting or running. But if there was rodent damage in that location, I would keep looking for more signs of it throughout the vehicle, mice can get into the smallest locations, usually you can smell it when they get into the interior of the vehicle, I cant tell you how many rodent nests Ive taken out of vehicles, probably hundreds, especially when I was working for a Subaru dealership that was out in the county. I was finding them almost everyday.

Br wire from the (ISC) Idle speed control motor position sensor - PIN 17 readings at ECM: volts stayed .4 volts with air conditioner off and air conditioner on. I know that the fan at the radiator kicked on but I'm not sure what the parameters are or how to know if the compressor was on, which was a parameter for the third measurement. Seems kind of mute anyway because 0.4 is below the allowable tolerance which the diagram indicated from .5 to 1.3 volts and goes up to .8 to 1.8 with air conditioner on and 0.9 to 1.9 with compressor on. The car engine RPM was idling at 950, dropped to 900 when I turn the fan on, and drop to 700 when I turn the air conditioner on, but the car never died out.
I have not been able to get the car to start since I did that test after turning the car off. The instrument warning panel lights come on when I turn the key on, and the car cranks every time I turn the key on, but it has not started since I did that air conditioning test. I will push it out in the sun and try to start it tomorrow. I have not used the air conditioner for over a decade unless I was at high RPM on the freeway or somewhere where I never idled because even 10 or 20 years ago it would almost die out when the air conditioner was turned on at idle, and sometimes it did die out and was hard to start.
There is a guard for the volume air flow inlet, but it was nowhere near where the actual opening was so I took it off from the manufactured location and put it right up against the opening and then I tied it in place to keep the rats or mice from accessing the filter in the volume air flow Component.

Okay, putting the guard in front of the air flow meter will effect air flow into the engine, in fact those air filter boxes are designed in a way that causes the air flow to be more turbulent,
It sounds like the idle speed motor might not be moving like it should, Try removing the guard from the air intake boot area, and see if it will start, technically pressing the gas pedal will open the throttle plates allowing more air in, if that idle speed motor is the issue.
For some reason the engine cannot handle any kind of load on it such as the AC compressor. You should see the AC compressor clutch cycling on the front of the compressor, Ive marked it here in red, that center part should be cycling on and off when you have the AC on.
but you shouldnt have to push it into the sun to get it to start, try removing the guard first.
Also take a look at the throttle plates, see if there is carbon built up around the edges of the plate, you can move it open by hand; this starting issue is probably a result of the ECT sensor being out of range during a cold start up, thats the main sensor the ECM is looking at for fuel delivery when the engine is cold,. So I think either moving it into the sun brings that sensor closer to a reasonable spec, or the ECM itself is warming up and has an internal problem on the circuit board, I assume you have another vehicle to get around?
Can you post a picture of the ECM for me, you dont need to unplug it or anything, I just want to see which type it is. If you have trouble posting it here for whatever reason leave me an email and Ill contact you for the picture.
I also question the condition of the ignition system, ie spark plugs and wires, possibly some clogged fuel injectors as well. or even old gas since youre having so much trouble starting it.

Two of the photos are of the engine control module both sides, two of the photos are of the throttle next to the idle speed control and the last photo is of the clutch or air conditioner part that you wanted me to look at because it is way down in there and I'm not sure when you say cycling on and off if that thing is spinning or moving in and out - I could not tell. Another strange thing that might be helpful is that the coolant temperature warning light, door ajar, brake and the battery warning light always came on when I turn the key on and now since we did the air conditioning test those lights do not come on when I turn the key on but after trying to start the car the lights then show up with the other warning lights (check engine, oil, seat belt).

The front clutch on the AC compressor should be spinning and cycling on and off roughly every 8 seconds on these older ones. I can definitely see that is a remaned ECM.
Removing the guard in front of the air flow meter and checking the condition of the throttle plates would be what I would do next, you'll need to remove the air intake hose that goes to the throttle body but that should only be held in place by a hose clamp.

Something to note, and I will post the air volume sensor operation below because it signals the ECM by Frequency not a voltage reading and the vortex or turbulence of the incoming air is very import for the sensor to read correctly, and the **guard being in the way is not allowing that air turbulence,
the ECM calculates the amount of fuel to be delivered from the air volume sensor, using the other sensors such as the IAT and other temperature sensors to adjust that air/fuel mixture depending on engine and outside temperature.

The Coolant temperature warning light is most likely happening because of that voltage variation. With only 3.8volts on a 5volt reference circuit for such a critical sensor, and the load that the AC compressor put on the engine, (even if it didnt turn on because the ECM will adjust the idle according to the AC pressure sensor), may have just plainly over worked some other components. Because the car is not driven much at all, thats one of the worst things for a vehicle, is to sit, it effects so much.

So from here we can either diagnose the no start condition by checking for ignition spark to make sure the spark plugs are even firing, you can see if it will start with the air intake system cleared of any obstructions, such as that guard, at least temporarily.

Diagram 3 below is some notes on your testing voltages, there are some sensors not reading correctly, The Baro reading should not have changed, since the key On values are different than the running values, I do wonder about this battery too.
But put the air flow guard back where it should be, check the battery voltage before starting the car, and see how low the voltage drops when cranking the engine. If it drops below 9-10volts during cranking its no good and needs to be replaced. A bad battery can cause Alternator problems that will eventually cause the ECM to fail.

The ECM I can bench test if needed, but low voltage to the ECM during running or a wire connection issue (corrosion) will cause voltage drop especially while running because of the extra electrical loads. Even though you tested the wrong pin, 19 instead of 17, the throttle position sensor is not reading correctly at full throttle.
These are probably all related. Diagram 4 is the ECM battery voltage pins and 5,6 are the Ground locations in the engine compartment to check for corrosion or broken wires, they should be cleaned as well.

The car cranks but it will not start, and it has only started doing this since the air conditioning fan and clutch were engaged. On the instrument warning panel lights, the door ajar light should be on and is not on and the brake light is on dim when it should not be on and the brake light goes bright when I engage the brake and sometimes when I turn the key on there are three lights and sometimes there are six lights and after turning the key to crank it defaults back to six lights in the instrument warning panel and all of this has started since you had me do the air conditioner test on the engine control module PIN 17 test that resulted in point 4 volts when it should have been .5 volts to 1.3 volts. I swapped the battery and the problem is the same. The five ground points that the diagram indicated as the eclipse engine grounding points all tested with what appeared to be the same appropriate ohms. Can there be a wire or wires from the air conditioner or air conditioning components that can tell the engine to shut down as soon as it starts (meaning it cannot ever start) and can be causing instrument warning panel light issues? Why is engine control module PIN 17 giving a steady .4 volts when it should have been climbing to .8-1.8 when the air conditioner was turned on. The air conditioner has been a problem with this car since before the engine control module went dead in January of 2013 and since ECM was replaced the check engine light to the best of my knowledge has been on. Many mechanics have looked at this car with this information, and either walked away scratching their heads or charged me money and amplified or increased the problems.
I remove the hose between the idle speed control engine position module and the volume air flow sensor, but you have to tell me why or what to do with it. I also remove the guard that was intended to keep the rodents out of the volume air flow sensor filter, but the car started many times with that guard in place and it still will not start now without the guard in place.

I wanted you to check the throttle plates for any carbon build up, and you cant get to them without removing the air intake boot. If the ISC motor position should move when the AC is on to increase the engine idle because of the load the AC compressor puts on the engine, try unplugging the compressor clutch, it has a connector that goes to the clutch on the front.
Its possible the AC compressor is starting to seize up or there is a problem with the Compressor clutch or Clutch relay. So unplugging it to begin with will take it out of the equation electrically.

There some electrical issues going on here, if you have lights that are dim, then getting bright and some on and off, thats a voltage loss somewhere.
And there is a reason the original ECM went bad in the first place too, this is an old vehicle, so things are going to have worn out by now,

The Brake lamp on the dash is triggered in two possible ways, either there is low brake fluid in the master cylinder or the Parking brake switch is engaged (diagram 2).
Checking the voltage level for the idle position sensor with the AC on shouldnt cause any additional issues. Its because we have started testing things and moving wires around and even the ECM connectors might have lose pin issues.

If the throttle plates look ok, and there isnt any black carbon around the edges of the plate, then just put the intake air boot back on and put everything back together.

Are you able to press on the gas pedal when cranking the engine? That will allow more air into the engine if the ISC motor is not moving its full range. Thats all the ISC motor does, its just moves in and out to open a port that bypasses the throttle plate and allows air in to control the idle. And thats why its position voltage should increase as well with the AC on, because its opening more to up the idle.

Diagram 4 are the Power and Ground wires at the ECM.

Sorry for the delay, but I have found some more diagrams that link things together, I will post them next.

So, these two first diagrams are for the Door Ajar lamp which originates from Fuse 19 10Amp in the dash fuse junction box, but what is interesting is in diagram 3 notice that Fusible Link 6 40Amp branches off and goes to the AC Clutch Relay, then also goes to that same Fuse 19 10Amp in diagram 4. So you may find a blown fuse that happened when the either the AC compressor Clutch came on, or something is wrong with the Relay that controls the compressor clutch. It does link together.
Diagram 5 shows all the fuse box locations Since there are 3 locations in the engine compartment and then one under the drivers side dash.
So with a test light hooked to ground, you should have power on both sides of each fuse. And check the fuse locations for any corrosion inside the pins as well..

https://www.2carpros.com/articles/how-to-check-a-car-fuse

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

Sorry, I did not get to looking at any of the fuses yet.
I'm not sure what constitutes carbon on the engine throttle plates because I didn't see any black, but when I ran my finger around the edges there was a blackish film on my fingers. The entire hose that goes from the volume air flow sensor to the throttle turns my hands black if I touch it. I unplugged the only connector I saw to the air conditioning clutch area; it was just a one wire connector (very difficult to get off)and it had a separate ground nearby. Did you tell me to replace the connector for the idle speed control motor position sensor, that was the one I sent you the photos of, but I do not know how to replace the connectors. I might need you to look at the distributor connector because I think it is worse because it fell off when I was trying to get the AC clutch connector off. I know this is a stupid question, but I need to know. You said to push the gas pedal when I try to start the car - does that mean I push the gas pedal before I turn the key, while I turn the key after I turn the key on All/any/some of the above or some other modification. The car still would not start today but it still cranks and has the instrument warning panel light confusions. I do not mean to leave things out but some things I forget to do or don't know how to do. I better send this before I fall asleep.

It's okay, I meant to push on the gas pedal while you are cranking to allow more air into the engine to help it start, the black stuff youre getting on your hands is carbon build up, if its all the way into the air intake boot, most likely its has contaminated the air volume sensor as well. But right now the harness connectors sound like they are in bad shape, they should not be falling off or loose in any way at all. That means you are probably not getting a crank or cam signal to the computer, both the ISC motor sensor and Distributor connectors need to be on solid and tight, or the pins inside the connector will not make any contact and nothing will happen. Cranking the engine over right now is pointless until you get those connectors repaired. If you are not familiar with wire repair or crimping new connectors on, it will take some time to explain it to you, send me pictures that I can clearly see both damaged connectors from the wire side as well as the inside pin side.
You can get new pigtails with a section of wires already connected to the pins but you will need to crimp the wires together in the correct places, and heat shrink them down to keep moisture out. I will explain all this, but see if you can even get new connectors for the Distributor and ISC motor position sensor. You may have to go to the dealership for this, I dont know, considering the age of the vehicle. But these repairs need to be done first.

Get a can of this electrical terminal cleaner, and these are heat shrink butt connectors, they crimp the wires together, and then you heat the ends and they will seal around the wires to protect from any corrosion. You can search you tube for any videos showing how to crimp wires together to get an idea of how it works.
This is an example of a pigtail replacement connector.

Photos of the harness connectors. I think the distributor and the idle speed control motor position sensor connectors are the same.,

The two harness connectors are so heavily damaged that it is difficult to determine the shape, but I believe this is the part number.

MG640547-5 6 Pin Female MAF Sensor And Ignition Distributor For Mitsubishi

And I attached a link to a photo of the actual harness connector.

https://www.aliexpress.com/i/2251832663961130.html?gatewayAdapt=4itemAdapt

There's another one at the same link that has the pins already connected with the wires.

No you don't want to have to deal with re-pinning the connectors, you need to get a connector with a pigtail, so a connector with wires already pinned into the connector like I posted. (1st picture) this is the type of connector you need to get; it will take you forever to rebuild a connector with new pins, and then try to stripe the wires to fit those pins, then get them into the new connectors making sure they make perfect contact. It will never happen. You have to have a lot of experience even dealing with the pins to begin with. Don't buy any junk connectors from Amazon or some other cheap site, they are going to be incorrect like always, go to AutoZone or some local auto parts store and see if they can get you those connectors with pigtails already connected, and crimp the connectors together.

With a connector that already has the wires installed in it, you just need to go wire by wire one at a time and use crimp connectors (2nd pic) making sure you have the correct wire in the new connector going to the old wire from the old connector. Thats the only way you will be able to do this,
The other issue you are having is the low reference voltage. And most likely a ISC motor that has carbon build up inside, like I said, all the black soot that is in the air intake boot and around the throttle plates is carbon build up, your intake manifold is probably full of the same stuff. But that low reference voltage is definitely a problem, Pins 8 and 20 at the ECM should have a full 5 volts or those sensors will not read correctly. It looks like the ECM in the picture isn't even bolted down. I can only go so far with this, have you checked the power and grounds at the ECM yet? Your original post was for these four codes setting, the ECT is the first sensor the ECM is going to use during a cold start.
And the engine needs air which the ISC motor provides, in the 3rd diagram below is the code setting criteria, the 3rd row over are the voltage levels that will cause that code, the 4th row over are some possible causes, same with the other codes,

You may need to have a mobile technician come out and look at the vehicle, not some shop where they don't know what they are even looking at. It will save you a lot of time and a headache. Just have a mobile tech come out, tell him about the low reference voltage, and the codes, let him figure out what's wrong, it will probably take an hour of diagnostic time, then fix what's wrong yourself, there are too many issues with this vehicle and possibly a bad ECM to figure this out on your own, I know you want to, but it takes years to learn how to properly diagnose these things, if I could I would come to your house and help. But that's not possible unless you live in NC. I'm helping with the relief work from the flooding in Ashville NC too. Bouncing back and forth here. It would just help you so much at this point to pay a mobile guy for an hour or two of diag time, just to figure out the issues. Where are you located?

I was hoping to remove the wires as they are in the connector and put them into the new connector since the connector is damaged and the wires probably are not - then I would not be stripping or connecting wires to wires.

Is it possible for me to determine if the car is getting fuel, spark, and Air while it turns over (I crank it by turning the key to the start position) to make sure that fuel, spark and Air are available for it to run?
I am in Daleville Alabama.

If someone could guarantee me that the car would run forever by guiding me through repairs and maybe even get the check engine light to go out, I would work with them, but I'm absolutely sure that that is not possible -working with anyone that charges money is catastrophic:
Kelley Blue Book shows the value of this car to be between $400 and $1,500, so I would be a fool to pay anyone to do anything since it may never run again and I might not even get $400 for it if it's not running - I might not even be able to donate it to a local used car dealer with a mechanic.
This car running is like a perfect and beautiful Ferrari to me, broken this car is like being stabbed in the back forever.
Mitsubishi does not even work on cars older than 2010, and they don't even know who makes the harnesses for the cars they sell now. There are hundreds if not thousands of functioning parts on this car that should be utilized until the parts have met a demise that is far greater than where this car and its parts currently are. The government should make every manufacturer of automobiles make sure that every car that is repairable is repaired or rebuilt if condition allows and to force manufacturers to focus on repairability and customer satisfaction.