HO2 heaters

There are two relays in that system, one is the main power relay (PCM) which is powered on all the time and provides power to most of the engine control systems. It also sends power over the purple with blue stripe wire to the O2 sensor heater relay mounted on the strut tower. That relay is turned on/off when the Black with orange stripe wire grounds it, that is connected to the PCM at pin 14. The relay supplies power to the sensor heaters on the purple and yellow and purple and blue wires. The only connection between the relays is the purple with yellow and purple with blue (they change color at the first connection).

Then what is the HO2S relay for that's in the engine compartment fuse box?

I don't see a second relay for the heaters in that box. Could you take a picture of it and post it? The attached is the OE diagram for that box.

Some one put a white piece of tape on the low speed fan relay and wrote HO2 on it and I was to stupid to realize the mistake. You were right. I'm all set now. Thank you very much for your help.

No problem. Wonder if maybe they were testing the relays and swapped the high for low and tagged the high relay to track it. Or it may have come from a different vehicle. Hard to say. I've seen more than a few odd things like that. Doesn't make you stupid, just dealing with what others did before you.

I finally got to drive the car on the highway for about a hour and there were some problems. It would not start off in first gear. If I put my foot into it, it would start in second and shift into 3rd but then no converter lock-up or 4th gear. One possibility is that the transmission range sensor seems to be out of adjustment since the back-up light only comes on when the shift lever is almost to the neutral position. Other than that do you think the VSS is bad or the ECM ?

Also the car is down on power.

I would start by adjusting the position sensor, that alone could cause the issues you have as the PCM doesn't know what gear the transmission actually is in other than what the sensor is telling it. So if the transmission is physically in say second gear but the PCM thinks it's in 3rd you get the power and shift characteristics of 2nd gear but the transmission won't act that way. Adjustment on them isn't hard but it's a bit of a mess as you need to disconnect the sensor, then use a meter to measure the resistance in the various positions. The reverse lights can help with this. Put the transmission in reverse, then adjust the switch so the lights come on and mark it, then adjust it so they go off on the other side and mark that position, now adjust the switch to the middle of that range. Then do the resistance testing on the indicated pins. If it's in range and works test it on the road.
If it still isn't correct then please ask a new question relating to the transmission and include the testing results and symptoms.

I detached the wires to pin 30 and pin 46 and took the resistance readings. They were good in all positions. Then I reconnected the wires and took a voltage reading from the pin 30 wire to ground and got the correct voltage readings in all positions.
Now when I put it into reverse it engages but after running about 5 to 10 minutes it starts shifting erratically and sometimes won't go into reverse. My guess is the shift solenoids are sticking. Should I change the transmission oil again? What about the PCM?

Do the reverse lights engage when in reverse now? If not it's possible there is an issue with the resistance readings at the PCM itself. That is what the PCM uses to adjust the shift points and characteristics. If the trans fluid was recently changed it shouldn't be the issue. However it could be internal to the transmission as it sounds like it's heat related. The solenoids can be affected by heat as well.

The reverse lights work when R is selected. All the resistance and voltage readings related to the neutral safety switch are nominal. This car sat for about 4 years so I would guess that the transmission solenoids could be gummed up. However I have other PCMs. Do you think I should try another one?

Okay, if it sat for that long it's likely that the seals and transmission parts are sticky or actually dried out. For that I would try adding some Lucas transmission fix additive. It should help bring the seals back to life. If possible run it some to get the transmission warmed up and circulate the fluid and add the Lucas. Then run it a bit more and see if it comes back. I've had good luck with it in vehicles that have sat a while.

Today I ran the car for about 20 minutes then shut it of and put in the quart of Lucas transmission additive and drove it for about an hour around town and on the highway. It really didn't seem to help too much. Maybe it takes longer to work. I noticed that normal acceleration was 2nd and third gear only. If I put my foot into it, first gear seemed to engage for an instant then right into 2nd. At full throttle it would shift back and forth between 2nd and 3rd. No converter lock-up or 4th gear. I was thinking of checking the turbine shaft speed sensor to see if it is wired properly.

It can take a while as it has to actually work on the parts chemically. After setting that long the end result may be that the transmission will need to be rebuilt. I doubt it's any electronic issue unless the PCM has an internal issue or the passages in the transmission itself are gummed up and blocking flow to/from a solenoid. It's why I tell people that leaving a vehicle setting for a long period will do far more damage than driving it. I have an older Blazer that has been setting for a while, it's currently waiting for spring to be stripped down and rebuilt using some "better" parts. While it has been setting the injectors have stuck, the brake master has failed and the transmission will barely shift and it ran like a watch before it was parked.

I don't remember whether I told you or not but I had to rewire all the sensors and PCM because all the engine wiring harness insulation had disintegrated. The previous owner didn't get the recall notice about that. By the time I had the problem, the harnesses were not available except as a custom piece at an outrageous price so I decided to rewire it myself for a retirement project. It was an extreme undertaking. I made many mistakes and had to re-do some parts. I used high temperature wire. There still could be some errors although I triple checked everything.

Nope. no mention of that. Whose wiring diagrams did you use? OE or other? I guess it would be possible for it to be improper in that case.

The wiring diagram I used was a Ford manual for Contour and Mystique, electrical and vacuum troubleshooting. Also I used Alldatadiy from the internet and a Haynes.

That should cover it. I just wondered if you used only one source as some of the non-OE have been known to have errors in them.

Today I didn't do anything except drive the car for about 45 minutes and for the first 15 minutes I had all the gears plus reverse. Then it went back to 2nd and 3rd plus reverse. Might be getting better.

Keep working on it and you'll be able to take it to the track... LOL

You know, it does handle very well.

Hi,

I noticed it's been a couple days since we heard from you. Has any progress been made? We are interested in knowing.

Let us know.

Take care and God Bless,

Joe

I've been driving it and the shifting has been erratic. A couple of times it started in first and didn't shift until 6,000 RPMs and I didn't have my foot in it. Then it would mostly start in 2nd and shift to 3rd. It wouldn't always go into reverse without moving the shift lever back and forth.

Drive it hard a couple times and see what it does, if it doesn't improve it will likely need to be rebuilt to replace the seals and clean out anything built up or sticking. Transmission fluid can become a sticky mess if allowed to set.

Do you have a diagram of the wiring that goes to the diagnostic OBD1 trouble code reader connector?

I found the diagram that I need.

Was going to say there are some of them on this site. At least Ford didn't pull the GM type stuff and make them a mixed system.

I found my old OBD1 code reader and it spit out about 6 faults but nothing to do with the transmission. So right now I'm working to correct these problems.
I am a snowbird currently in Florida with the wife and we will be going back to New Hampshire the middle of April. I don't know how far I will get with this car but there is always next winter.
In NH I have two older cars, an 1987 Mercedes 190e with a diesel engine from a 300sd and an 1988 Honda Civic with a 5.0 Ford V8 mounted midships driving the rear wheels. Runs like a rabbit.

The Civic sounds a bit dangerous. LOL

What codes did you pull?

Joe

This car was built in October 1994 so I was told about 15 years ago that it used the Tempo/Topaz code system.

637 TOT sensor voltage above max voltage
327 EVP low
519 power steering unplugged
563 high speed fan
593 OH2 heater circuit bad (fixed)
341 octane circuit open (next)
551 intake runner circuit open

You have quite a list. The definitions for the codes are accurate. The idea that that transmission is giving you trouble is likely related to the temperature sensor. Have you done any checking?

Since I jumped into this part way through, can you tell me the ultimate goal? There seem to be a few different concerns.

The ultimate goal is to get this car running smoothly. I have found some wiring mistakes and been correcting them. Now I'm trying to find the octane adjust circuit.

Hi,

Take a look at the attached pic. Let me know if it helps.

Joe

Yes, that helps. Thank you.

Hi,

No problem. Let us know how you make out and what you find.

Take care,
Joe

I found some components were miss-wired or had one wire not connected. I had to take out the PCM connector to make these wiring changes. Now I can't get it back connected to the computer. The 6 mm bolt will not thread into place.

How were they repaired? Is something preventing the connector from being seated? Check to make sure none of the pins were damaged or bent.

Joe

It's my stupidity. The PCM had moved back because the clamp is missing so I made a new clamp and pushed the PCM into position. The connector went right on. Got too tired to try the engine. Tomorrow.

Hi,

It can happen. LOL Let me know how it runs. Hopefully, it will be better.

Joe

I "fixed" it real well. Now the fuel pump won't run unless I ground the wire from the PCM pin #22 that comes from the fuel pump relay. But then of course it won't shut off. Exactly what tells the fuel pump to turn on and off? I don't see any pressure switch. Is it current draw from the pump. Help.