If all the wiring checks out then it sounds like a valve body problem to me. The P0753 code descrbied exactly your problem, something with the 3-4 shift solenoid. (The shift solenoid A is the one that makes it shift from 3rd to 4th (OD)) Have the shop focus on the wiring first for that solenoid all the way from the PCM to the valve body.

 

Okay, this weekend I changed the belt tensioner and while I was at I reset the computer. Before this the code would flash every time OD tried to engage. Now it is intermittent. I drove for approx 20 hgwy miles until it flashed. I then pulled over, shut the engine off and then drove with od off for about a mile or so then turn od on and it hasn't messed up since. What are the chances that this is a computer problem. The only thing consistent, is that it flashes inconsistent.

 

It's a possibility. The PCM is what controls the transmission shift solenoids also. Ways to check is put a multimeter on the 3-4 shift soldenoid wire coming out of the PCM and connect the other side to ground, set it to resistance and when OD is suppose to engage the PCM will ground that wire. It should be a constant closed circuit in OD.

 

makes sense to me, the problem is I only have a 30-40 dollar sears multimeter. I don't want to toast the computer, also my leads are only 3' long. How would I drive and check this at the same time?

 

Resistance setting shouldn't output any voltage unless you have it set to test diodes. I've seen a friend install a TQ lockup switch and did it wrong by adding 12V to the PCM signal wire so it actually unlocked it, didn't fry anything.

Anyways, I'd find some random wire, get 1 end on the 3-4 shift signal wire, then run it inside the cabin (just shut the door on the wire), and connect that to one of your multimeter leads, the for the other lead just connect to something grounded inside. What you want to watch for is at about 40-45mph when the OD engages, or should engage, you want to see a constant closed ground, if it's jumping around then your PCM is most likely bad.

If all checks out, move down to the actual shift solenoid connector (just where ever it plugs into the outside of the transmission) and see if the wire from the PCM to the solenoid is good and if you're getting constant 12V (key might need to be on or car might need to be running for that) on the other wire going to the solenoid. Check out the service manuals on these forums for wiring digrams if you need to locate anything.

Hope this helps.

 

Also it just crossed my mind, if the trans relay in your PDC is not working, your OD solenoid won't get any 12v power. It will shift all the gears fine but the TQ will not lock up and OD will not engage, and probably some other stuff won't work, could just be a bad relay for all we know. Swap the relay out with something like your horn or A/C clutch and give it a test drive. Check out all that wiring for the relay too since you have the volt meter out.

 

Okay I talked too a few shops today that repair and tune pcm's. They said to look elsewhere that it is not a pcm problem. Kind of surprised me. I talked to the shop that rebuilt the trans, and they want $200 to replace the wiring harness from the pcm to the trans. How hard would this be to do myself? I'll spend $50 on a part, if that will fix my issue. I'd rather do it myself than pay the shop (especially since I'm suspicious of them anyway).

 

Check out and trans relay and wiring for that first before you get into the high $$ stuff.

 

I swapped the fuel pump relay and trans relay for a test. Should know something if its the relay in the morning lol.

 

Okay, swapped the relays and ran great for 2 days. Then tonight code flashed again. Haven't had time to try to ohm anything out yet unfortunately. I have come to the realization on something though. When you start a normal fuel injection engine rpms rev to approx. 1500 then settle out. Well, everytime it has flashed a code the rpms barely went up to 1000 on initial start up. Could be a coincidence.