92 Trans Sport (3800 engine, 4T60E transaxle) odd electrical problem


This happened last weekend once, and has done it several times since then. The van runs and drives beautifully, and everything works.

Except several times when it is started (cold or warm, does not matter), I get a SES light. The power windows are dead. The heater blower is dead. The transmission solenoids will not activate (I put it in gear and it acts like it is almost out of fluid, and the fluid is fine). The radio works. The power locks work. The engine starts, runs, and revs perfectly normal. I asked the wife to check some other accessories to see what else works and doesnt work when it does this.

It only does it at startup, never when it was already running. Shut it off and restart it, and it is usually fine. But sometimes it takes a few times of restarting it to make the problem go away. Everything is consistent, it is one problem. Once I get a successful restart, everything immediately works perfectly and it drives and shifts perfectly like nothing ever happened.

When I check the codes, I get a code 21 (TPS high voltage) and code 56 (quad driver B).

In the past, about every 1000 miles or so, I have gotten a code 21 while driving, the cruise would drop out and the SES light would come on. Then it would go off and the cruise would work fine again. Testing the TPS turned out fine. So the code 21 may be from this. It did it once the other day.

I went to check out the ECM, and I see whatever supports it at the bottom was broken off (and had been probably for years by the looks of it) so it was supported by the floorboard. I checked for loose connectors, and nothing was loose, but I reseated them all anyway. Yesterday it was fine. Today it acted up once.

Could a loose ECM connector do all this? Or is it most likely something else? I know the quad driver powers the transmission solenoids, but how about the power windows and heater blower? I have a factory service manual, but I am stumped at what it could be that is causing this. It is perfectly consistent. When it acts up, all 3 things always wont work (heater blower, trans solenoids, and power windows).

Any other ideas? Any other wiring I should be looking at?


An idea. All of the dropped circuits would be dropped during the starting process as unneccesary loads. It is possible that the ignition switch is not returning from the start position completely or the ignition switch is faulty.

Out on a limb but hoping to help


Thank you for your advice. I hadnt thought of that, but it makes sense. I looked in the manual for the ignition switch circuitry, and all the things that were not working were wired strictly to RUN mode on the ignition switch.

I looked at the ignition switch, and even before removing it, I noticed the orange RUN wire looked dark like it had been slightly burnt. I pulled the ignition switch and the RUN terminal was quite melted. So Id say the switch was bad. I swapped in a switch I saved from a junked Celebrity, which was the same model switch, and during several starts it seems to work fine now. However I realize that replacing the switch is only half the problem. I need to find why it melted in the first place.

The guy who had the van before me had replaced the ignition switch. I dont know how it went bad. But he didnt seem to know what he was doing. He broke the shift indicator cable. He hadnt adjusted the switch, so to start the van, you had to turn the key all the way to the stop then it barely went into start mode. He also left out the lock ring in the steering column, maybe he thought he had to replace the switch that way first. I adjusted this switch and it starts much easier, and still turns back into accessory mode.

Maybe the switch being out of adjustment made the switch heat up. Not sure. Ill have to keep an eye on it.