Need help troubleshooting my trans. :(

[93ParkAvenue]

Never heard of a fuse acting that way but we shall see. I'm not holding my breath though.

[93ParkAvenue]

Ok, more data. Drove car yesterday for a couple of hours. I lost overdrive less than 5 miles of driving. It drove probably another 45 minutes with no additional issues.

Then, the check engine light came on for a while. Car didn't seem to be driving any differently.

Light went off for a while.

Then came on again and that's when I lost 1st again. Came home and pulled codes: DTC - 21 Throttle Position sensor error (signal high), DTC - 39 TCC error, DTC - 56 Quad Driver Module (QDM B) error.

I've got to run to town for a bit but will be coming back home to research this a little bit. Just wanted to post it before I left.

[robertisaar]

your DTC 56 is probably causing DTC 39.... DTC 21 looks to be a "bonus".

did it kill the fuse again?











these should help troubleshoot the DTC56.

[93ParkAvenue]

Thanks for the diagrams. Yes, the fuse did blow. I want to say the light came on at highway speed so I would have been in 3rd. Not sure if that matters.

Do you happen to have one for DTC 39? DTC 56 chart says go to DTC 39 first. If you there is a library of these online, can I look at them myself?

[pocket-rocket]

If you bought alldata or Mitchell, yes.

I would suggest scouring the net for the Helms manuals got your car. They are the same manuals you would find in aGM dealer. I have a set for my car and they are the best. Tons of information... The two manuals together are about 3-4 inches thick...

Sent from my HTC One X using Tapatalk 2

[robertisaar]

http://i.imgur.com/Dnjtk.png

http://i.imgur.com/j3HVb.png

it wants serious use of the tech1....

[93ParkAvenue]

I depinned the blue wire at position B and plugged back in. Replaced the fuse and started car. The fuse blew immediately. Disconnecting that blue wire still doesn't exclude the tcc solenoid from being the potential problem does it?

[robertisaar]

interesting result... the fact that it blew with the TCC PWM solenoid disconnected means while it COULD be a problem, there is most definitely at least one more problem that's connected to that circuit.

after starting, 1st gear is both shift solenoids commanded on, so it sounds like one or both of those it what's doing it. the TCC solenoid wouldn't get commanded on yet, so that's probably not the issue. otherwise, the only other possible causes are from the high and low speed cooling fan relays or the TCC/brake switch.

know how to check the resistance of the shift solenoids?

[93ParkAvenue]

Not sure how to check the resistance. An assumption would be measuring between the pins and ground.

[robertisaar]

close. it's between the pin for each solenoid and the +12V pin on the trans connector plug. the ECM switches the ground, so the constant positive is the one you want to check against.

[93ParkAvenue]

Alrighty, will report back.

[93ParkAvenue]

Shift solenoid "B" = 39.1 ohm
Shift solenoid "A" = 39.4
Tcc apply solenoid = 17.6
And I checked pin E because the diagram called for 10 ohms(right?). I got an open reading.

I supplied 12 volts to the 3 solenoids I mentioned. I got clicks on A and B shift solenoids, but no audible click on the tcc solenoid.

I did not check the tcc pwm solenoid at pin B. Should I?

[robertisaar]

if the trans was warm/hot when you checked, the SSA and SSB are within range, but TCC apply is not.
if the trans was just air temp when you checked, then SSA, SSB and TCC apply are out of range.

the 10 ohms in the diagram was referencing the TCC PWM solenoid. look at the resistances of the shift solenoids above and you'll see it. pin E is the 12V feed for the solenoids in the transmission, so getting an open reading to ground would be normal

it wouldn't hurt to check the TCC PWM solenoid.

[93ParkAvenue]

Trans was cold. Unfortunately, I drained the fluid without thinking to check resistances hot.

Is the lack of click from the tcc apply solenoid also an indicator of a fault? I bought 2 solenoids but had to wait for them to come in. Wish I had just gotten a 3rd in case. Is the 17.6 ohms low enough to cause a problem?

[robertisaar]

well, as the trans fluid heats up, it heats the solenoids as well, which causes the resistance of the windings to increase, which means less current gets sent through. that essentially means that they'll be able to do less work(withstand as much line pressure) before they start moving into their unenergized positions while still being energized. with the shift solenoids, that means you'll actually start slipping between gears. with the TCC apply and PWM solenoids, that means TCC slippage.

i would THINK you would be able to hear the TCC solenoid, but i'm not really certain, seeing how it requires line pressure to actually force the TCC clutch to move.