Convertor Lock up troubleshooting

Black Demon

Brick Maker
Need some help with a D5 convertor that won't lock.

1. Established that all electrical contacts are in order.
2. Dropped pan and checked solenoid. It opened and closed
when I pulled it out of the transmission and put power to it.
3. Reinstalled it. Transmission shifts well in all gears just no


What is my next step in tracking this down?
Is this usually a convertor problem or a pump/pressure problem?

Thanks for your help. I am a new GN owner, and the support you guys give is invaluable!
Don't you hate it when someone answers your questions with more questions?

Sorry, but more information would help.

Have you verified that the ECM is indeed providing a signal for it to lock? Have you tried to lock it manually via the ALDL connector?

What is the history of the transmission/converter in your GN? Has this converter ever locked since you've owned the car? If not, there are a host of things that may be amiss: TCC valve stuck in pump, physical problem with the pump itself, failed/missing input shaft o-ring, bad converter.
Greg, thanks for the quick response!

I bought the car in August after the engine was freshened. The convertor did not lock then, but I did not realize that until later. Using turbolink when the chip locks (thrasher) there is no rpm change and no "extra gear" feel. I did ground the ALDL connector with no luck, and then checked all the wiring as posted above. I did install a B&M Transpack and cooler in September just to be on the safe side. I don't know the true history of the transmission other than it had 100,000 miles on it with a history of the fluid changes.

Here is a test you can do to narrow down the cause of the problem. It's a bit of a PITA but will go a long way in helping to diagnose the problem.

Pull the pan and the TCC solenoid out. Above the solenoid, resides the TCC apply valve. Remove the retaining ring, washer, valve and spring. (Here's where you'll find out if the valve is stuck. If it is stuck, that's a problem.)

Now, put the valve back in first, then the spring, washer and retaining ring. Button it up and pour in the fluid. (If you use a real clean drain pan, just pour the same fluid back in.)

What you have done here is effectively applied the TCC valve while bypassing the entire electrical system. If the transmission and converter lock-up mechanicals are OK, when you place the car in gear (fwd. or rev.), it'll kill the engine because the TCC will already be applied.

If the car doesn't drive any differently in this configuration, that's bad news as there is something amiss in the trans/converter as mentioned above. If the TCC now works, there is a sneaky control problem that needs to be rectified but at least you'll better know where you stand.
Addendum to above


I have a feeling I am going to wind up at a local transmission shop. I am looking to be armed with as much knowledge as possible-mainly so I can make sure the repairman knows what he is doing and he is capable of diagnosing this problem. Based on what I have read, good mechanics for the performance 2004r are few and far between. Some of my local TR buddies have pointed me in the direction of one shop here in Augusta. But, let me ask you: If I brought my car to your shop and explained everything above to you, where would you start on your diagnosis??

Thanks for your help, Mike
Not unlike you've already done.

I'd check fluid level first, then make sure the TCC connector is plugged in.

I'd then verify that 12 V is present at terminal A and that the ground circuit is intact. I'd then measure solenoid resistance via the outer case connector to verify it and the internal wiring.

If it checks out electrically, then the pan would come off and I'd look into doing the procedure outlined in this thread to narrow down the problem area.

Good Luck with it!