Just a few days ago my o/d off light came on at the same time HARD shift to 2nd. Pulled a P0743. I'm not too great with auto maintenance, however I do have a vast knowledge of electronics and circuitry. Can anyone tell me what test points I can check for open/short, and grounds for my tcc solenoid? Last year my MIL light came on and kept popping fuse #32, dash indicator flashed "trans fault" I found a chaffed ground causing that issue, could these be linked? Also, have no idea of it's relevance but it seems most of the time the tranny starts giving me trouble, my E-brake light is on as well. I've hit what I believe is the toggle for the e brake and it stays on. Once I get up to 45-50 mph it runs great, but slowing down it doesn't seem to want to downshift. I got all the way to work today (60 miles) with no problems, until I put it in reverse and E-brake, MIL, o/d off, and trans fault all showed up together. No clue on transmission type or any of that, but if it's needed I will find it somehow, if it helps it was an old meter reader truck, BARE stock everything. Only hard driving I have done with it is going in reverse for fairly long distances. (1000 ft) (I work in telecom, it's faster than finding a driveway in back road Indiana) that's all I can think of that is relevant, probably too much, but if thee is anything else that needs to be known I'll figure it out. ANY help would be so greatly appreciated, even just general advice so if I take it to a trans shop I don't get robbed!! Lol Thanks Guys!!!


Dan

 

It's a 4R70W transmission. I don't have a wiring diagram for that truck, you need to find one. Check the continuity of the wiring from the PCM to the TCC solenoid in the transmission. Also check the circuit for shorts to ground and shorts to power. Keep in mind it can be an intermittent problem. If you don't find anything static you'll need to check while moving/wiggling the harness.

 

Mark,
Thank you for the reply! It's Definatly intermittent, although it's starting to be more of a constant, there are times the "service engine" and o/d lights don't luminate. I'm hot on the trail for a schematic, is there any way to test the solenoid without getting into the transmission? I'm waiting on a call from a transmission guy to do any repairs, but if at all possible I'd like to diagnose the issue myself to avoid any "repairs" that aren't needed. Thaks again for the reply!!!

 

Once you have the wiring diagram you can put 12 volts across the solenoid pins on the transmission connector and listen for it to click. It's easy to hear as long as the engine is off and you're under the truck.