Will not start, codes P0122 and P0622

P0122 - Throttle/Pedal Position Sensor/Switch A Circuit Low Input
P0622 - Generator Field "F" Control Circuit Malfunction

Neither code is related to the MAP sensor, and neither one will prevent the engine from running. Is it possible you disconnected the battery for the recent service? If you did, idle speed is going to be so low that you may have to hold the accelerator pedal down 1/4" for the engine to run.

First, listen for the hum of the fuel pump for one second when you turn on the ignition switch. If it isn't starting up, banging on the bottom of the gas tank often jars them enough to get them started. That failure to start may occur the next time you try to start the engine, or it may not occur again for months, but for that problem, the pump will eventually have to be replaced. When it does start up, it will rarely stop while you're driving.

What led up to these fault codes? Did the Check Engine light turn on while you were driving? What made the code erase? That doesn't happen on its own.

I'm going to assume the battery was recently disconnected. That results in a loss of memory in the Engine Computer. Most of the sensor and fuel trim data will be rebuilt as soon as you start driving, without you even noticing, except for "minimum throttle". Until that is relearned, the engine may not start or run unless you hold the accelerator pedal down about 1/4". You won't get the normal idle flare-up to 1500 rpm at start-up, and it will tend to stall at stop signs. Once any other problems are solved, to meet the conditions for the relearn to take place, drive at highway speed with the engine warmed up, then coast for at least seven seconds without touching the pedals.

The voltage regulator is inside the Engine Computer. That circuitry is in series with the field coil in the alternator. The regulator controls the amount of current flow through the field winding. That controls the strength of the electromagnetic field, and thereby, the amount of alternator output current and voltage. At maximum output, field current is still less than three amps, but it would take a pretty hefty switching transistor to control that. Instead, they use "pulse-width modulation" where they switch the three amps fully-on, then fully off, about 400 times per second. Both modes result in 0 watts which translates into almost no heat build-up, and the ability to use a small, inexpensive switching transistor.. Normally, when there's a defect with the voltage regulator's circuit, to include the wiring to the alternator, the typical fault code is "Field current not switching properly". Code 622 is different. As with all other codes, they never point to a part that must be replaced. This is a perfect example of where the code just tells us the circuit that needs further diagnosis.

The place to start with this problem is to measure the battery voltage, first with the engine off, then with it running. With the engine off, battery voltage must be 12.6 volts. If it's near 12.2 volts, it's okay but fully discharged. Charge it at a slow rate for a couple of hours, then check it again.

Next, measure the battery voltage with the engine running. It must be between 13.75 and 14.75 volts. If that is okay, that only means it is okay to continue with the rest of the system test, but that requires a professional load tester. The people at any battery store can run that test for you. Many do it for free because it only takes about a minute.
This article may be of more help:

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

also check out this video:

https://youtu.be/Z-p4dMJUpUw

I don't recall ever running into code 622, so I'm interested to know what the charging system test shows up. I have a suspicion it might find excessive "ripple voltage" which would point to one failed diode of the six in the alternator. That will also reduce the maximum current it can develop to exactly one-third of its rated output current. The voltage regulator may have a hard time adjusting system voltage when it's trying to follow the ripple voltage, and that might be the cause of code 622.

How did you determine only two cylinders are firing? Some engines use coil packs where each ignition coil fires two cylinders at the same time. A failure of one of those results in two dead cylinders. A failure of two coils is rare because the assembly gets replaced as soon as the first failure occurs. Your engine uses individual ignition coils, so any failure affects just one cylinder. To have multiple failures at the same time would suggest something else is responsible. The first thing that comes to mind is a corroded splice in the wiring harness. A common 12-volt source feeds the injectors and the ignition coils, among other things including the alternator's field coil. A corroded splice in the right spot could would affect just the items after that point. Low system voltage could also result in multiple cylinder misfires, but it's more likely the symptom would simply be a failure of the starter to crank the engine.

That common 12-volt source is switched on through the automatic shutdown, (ASD) relay. Failures of those are not at all common, but to rule out arced or pitted contacts, you might want to switch it with one of the others like it. That circuit also feeds the oxygen sensor heaters. Wiring harnesses for those have been known to fall down onto hot exhaust parts on some car models. If that heater wire melts and shorts to part of the exhaust system, a dead short will cause a fuse to blow, then you'll have a crank / no-start condition. If it isn't a solid dead short yet, it could result in lowering circuit voltage enough that some injectors and / or some ignition coils don't fire.

Check out as much of this as you can, then let me know what you find. If we have to pursue this further, do you have access to a scanner?

Dandy video. It has to be running on more than two cylinders. As a point of interest, we were learning about automatic idle speed motors at a Chrysler school I attended back in the early '90s. The instructor was showing us how much control the Engine Computer had over idle speed. Part of that demonstration was performed on an 8-cylinder Jeep engine. He unplugged a fuel injector, idle speed dropped, the computer saw that, and increased idle speed back to the desired speed. Each time he unplugged another injector, the computer brought the engine back up to speed. Eventually he had seven injectors unplugged. Obviously the engine was running very poorly, but it was still at the correct idle speed, and the AIS motor was not yet at the end of its travel.

The computer is also going to detect the misfires and set diagnostic fault codes indicating which ones are not firing. You can feel the misfires because crankshaft rotational speed slows down when a misfire occurs. That is the same way the computer knows which cylinder is misfiring. It knows where the crankshaft is when it slows down momentarily.

There's two things that can block a misfire code from being set. One is when there are multiple cylinders misfiring at the same time, the computer may have trouble figuring out which ones are affected. You're more likely then to get code P0300, multiple cylinder misfire. We have to look at what all of those cylinders have in common. One thing could be low fuel pressure. Most people think of the computer first, but in fact, it has six individual ignition coil driver circuits. Computer failures are not at all common, and to have even one driver circuit fail is almost unheard of, let alone multiples at the same time.

The second thing is for any fault code to set, there is always a long list of conditions that must be met, and one of those conditions is certain other codes can't already be set. The best example of this is when the engine has been off for at least six hours, the computer knows the coolant temperature sensor and the intake air temperature sensor had better be reading the same temperature. When they are not reading the same when the engine is started, the computer has ways of figuring out which one is wrong or if it just needs to relearn or update their values. No two sensors are ever exactly alike, so to prevent needing to make all kinds of adjustments when a sensor is replaced, the computer is designed to learn the personality of a new sensor. There are other "hard" defects that will result in a code being set, but in this example, if a code is already set for the intake air temperature sensor, the computer knows it can't rely on its readings to use for comparing to the coolant temperature sensor. Other than those hard defects, like cut wires, the computer will suspend tests related to sensor calibration, meaning signal voltages it expects to see during normal operation. It still has learned data stored for the CTS, so it still knows coolant temperature, as long as you don't replace that sensor. If you do, it might see coolant temperature as being slightly higher or lower than it really is, but that won't cause a fault code to set.

A similar story can be told for code P0622. Technically 13.9 volts is in the acceptable range, but it is still on the low side. We'd like to se it closer to 14.5 volts. We still don't know the cause of code 622, but that could be on the list of codes that can't already be set when running tests for misfires. It's possible the low or unstable charging voltage could mean the ignition coils are developing weak spark, and as far as the computer is concerned, multiple cylinder misfires are to be expected, so it refuses to set misfire codes because those could be misleading or confusing and make diagnosis take longer.

The first thing I would look at is fuel pressure with the engine running. Normal is:

Fuel System Pressure. 400 kpa ± 34 kpa (58 psi ± 5 psi)

The next step would be to use the scanner, under the "Actuator" test menu, to fire each ignition coil one at a time. With this type of coil, you'll have to insert a screwdriver to reach the terminal, then watch if spark jumps from the screwdriver to the engine. Without that extension, spark voltage is likely to not be high enough to jump that far. This test will verify each coil is okay, along with the individual driver circuits in the computer.

Next would be to look at the signals coming from the crankshaft position sensor and the camshaft position sensor. Unlike most other sensors where the acceptable range of signal voltage is from 0.5 to 4.5 volts, these two develop signals that switch from "low" to "high", typically from close to 0 volts to close to 5 volts. The exact voltage is irrelevant. These are used for timing, so it's only the transition points that are critical. By the time the diagnosis has gotten this far, we're looking for something unusual or uncommon. Most newer scanners can graph these signals, but they occur too fast to watch. Instead, there is usually a "record" feature that lets us record a few seconds of sensor data, then we can play it back slowly later to see what happened. As an example, crankshaft position sensors on some older engines needed to have their air gaps set very precisely. That was very easy to do if procedures were followed, but I have been known to be arrogant enough to not need those procedures. If the air gap is wrong, it can result in intermittent stalling, or it could be just on the edge of reading or not reading the notches in the flex plate that the sensor uses to generate its signal pulses. That could result in the computer not seeing when to fire some injectors or ignition coils.

Your crankshaft position sensor and camshaft position sensor have mounting flanges that eliminate the need for setting the air gap manually, but who is to say someone didn't replace one in the past and left the mounting bolt loose? That would be the type of unusual thing we would be looking for.

I wouldn't worry about any of those codes. We'll take care of those later.

Only running for two seconds is what happens when it's in theft mode. Try locking and unlocking a front door with the key to reset the anti-theft system, then try starting the engine. Remember to hold the accelerator pedal down 1/4".

There's two ways to start this diagnosis. The best way is to use a scanner to view the states of the crankshaft position sensor and the camshaft position sensor. My Chrysler DRB3 shows them as "No" or "Present" during cranking. If one is listed as "No", the circuit for that sensor is what needs further diagnosis.

A less-effective method is to monitor the voltage coming from the automatic shutdown, (ASD) relay. That will be the wire that is the same color at every injector and every ignition coil. On your car that's a dark green / light green wire. Test lights are more accurate than digital voltmeters for this test because voltmeters don't react fast enough. You'll need to poke the probe through the rubber seal alongside the wire. You should see the test light turn on full brightness for one second when you turn on the ignition switch, then it will turn off. That proves the ASD relay is okay and the Engine Computer has control of it. What's important is the light should turn on again during engine rotation, (cranking or running). If it does not, the signal from one of those two sensors is not showing up at the computer.

When the ASD relay doesn't turn on during cranking, there won't be any injector pulses and the ignition coils won't fire. The fuel pump still ran for that initial one second, and since no fuel is leaving the injectors, fuel pressure will remain close to normal. Failure of the ASD relay to turn on is responsible for perhaps 95 percent of crank / no-starts. When it does turn on, those no-starts are caused by a problem in the ignition system around two percent of the time, and the fuel supply system about three percent.

Almost all fuel supply problems are caused by a fuel pump that doesn't start up when you're cranking the engine. You can verify that by not hearing it's hum for that one second when you turn on the ignition switch. Dead fuel pumps are caused by worn brushes in the motor. They can often be started by banging on the bottom of the gas tank. Once they're running, they will continue to do so until the engine is stopped. They could fail to start again the next time, or that may not occur again for months. Chrysler fuel pumps rarely stop running while you're driving.

Failure of the ignition system itself is pretty much limited to a broken wire feeding the ignition coils. All six coils and all six injectors are protected by the same fuse, so if that fuse is blown, you won't have 12 volts to any of those places when checking ASD relay operation with the test light. There's six individual driver circuits in the Engine Computer for the six ignition coils, and six individual driver circuits for the six injectors. Failure of just any one of them is not common, but that would result in a single-cylinder misfire. Failure of multiples of any of those things at the same time is even less likely. The only thing that will affect all 12 driver circuits is the loss of one of the sensor signals, and the ASD relay isn't turning on during cranking.

I've never watched timing advance during cranking, so I don't know what normal is. Timing advance can be confusing anyway. While running, you can't get a signal pulse from the camshaft position sensor, then have the Engine Computer fire an ignition coil ten degrees before that. It's too late at that point. Instead, what they do is start out with a high amount of timing advance built in mechanically, meaning the signal pulses show up well ahead of top dead center. The computer calculates a desired amount of delay, then it fires the ignition coil. For example, a typical amount of advance to start with is 35 degrees. If the computer waits for 30 degrees, then fires the coil, you'll have five degrees of timing advance. Where the confusion comes in has to do with what the scanner is showing for timing advance. Is it showing the 30-degree delay or is it showing the five degrees actual timing advance? In fact, we don't need to know that it starts out with 35 degrees, and it's not important to know how many degrees of delay it has calculated. It's the five degrees we want to know.

I suspect you're seeing 0 degrees timing advance because less advance makes for an easier engine to crank and get started. It will jump up to around perhaps ten to 15 degrees when it's running.

You need a scanner for that. It will have some provision for indicating whether or not the signals are showing up at the Engine Computer.

The earliest engines starting in the late '80s required signals from both sensors for the engine to start and run. If either signal cut out while driving, the engine would stall. Beginning somewhere around the early 2000s, both signals were still needed for the engine to start, but once it was running, if one signal was lost, it would remain running on just the one sensor. There was a back-up strategy to time the injector pulses and ignition coils on the same sensor.

Many of the more-expensive scanners also have graphing capabilities. You select the signals you're interested in, then you can see what they look like on the chart. Cam and crank sensors develop a square wave that switches from near 0.0 volts to near 5.0 volts. The actual voltage is not important, but there is a transition period that will confuse the computer if the voltage falls within that mid range. For example, does the computer interpret 4.0 volts or 1.7 volts as "high" or "low"? If the air gap is too big, or the sensor's internal magnet is weak, it may be unable to pull the signal down to 0 volts. Suppose the computer sees anything lower than 1.00 volt as "0.0" volts. That's perfectly normal, until the signal shows up as 1.01 volt. The next time it might show up as 0.99 volts. These are right on the edge of being seen as acceptable or lost.

Instead of a weak signal from the sensor, there could be corrosion between two mating terminals in a connector. That corrosion adds resistance which reduces the signal voltage seen by the computer. Moisture, vibration, and heat all affect how much that resistance affects the strength of the signal, so those are all potential factors in intermittent loss of that signal. We would see that on the graph as the signal voltage not reaching close enough to 0.0 and 5.0 volts.

Can you tell if that gas smell is coming from the tail pipe, or if gas is leaking on top of the engine? There were two problems in the late '90s with gas leaks. One had to do with gluing on reinforcement strips on the sides of the fuel rails to prevent cracking, and the other had to do with injector o-rings that would shrink in cold weather and leak. The o-rings usually leaked slow enough for the gas to evaporate before you'd see wet spots, but you would still smell it. There was no 2.7L yet at that time, and I would suspect those problems were addressed in newer cars like yours. This was handled before I left the dealership, which was in late '99. If the injector o-rings are leaking, fuel pressure will bleed down when the engine is off, then you'll have an unusually-long crank time to restart the engine.