mjm-1957

We change a lot of starters on those trucks at work.

Pin 14 is circuit 2500 dark blue wire is high speed communication circuit, you were correct, pin 13 is blank on your model,sorry about that. If I could post the schematic you would have seen that. These old eyes aren't as sharp as they used to be. Glad ypu got it going.

Pin 13 is high speed communication circuit 2501. I cant figure out how to upload the schematic. If you have access to service information from GM the document ID number is 3627766. That should get you talking with the TCM again.

Make sure the connector at the transmission is fully seated and there are no bent or backed out terminals, the scanner should see the TCM at start up.If that checks out okay make sure the passthru in the case is fully seated and that the retainer is fulled locked.It should snap and click into place when fully seated.

Voltage drop both battery cables, anything over half volt and they should be replaced. An extremely common problem on those trucks. We change a lot of them at work.

What time did you start drinking today if you actually think GM makes 20,000 in profit on the sale of these trucks?I work in a GMC Buick dealer and can tell you you are slightly off in your arithmetic.

Are you talking about the knuckle? The hub has the bearing in it.

Timing chain.

Not stock, I have the same truck and it doesn't have them.

Have the dealer drive it with GDS 2 installed and command the tcc off 100% and note if the shudder still occurs. I am bettting the 456 clutch is slipping, not the converter. Three defective ones in a row??? Doubt it. I am the transmission guy at a GMC Buick dealer and have seen this before. They can also monitor the slip speed with the GDS while commanding the TCC on 100 %, will tell them which way to go.

It is a LIN bus communication error with the ECM. Bring it back to the dealer and let them fix it.

Welcome to GM. I have a stack of bad fuse boxes under my bench for all sorts of problems. I keep them for all the fuses and relays as spares.The high speed wiper relay is also internal and goes bad quite often. That fuse box is not cheap either.

Those numbers you listed are just the codes for recalibrations that are done and submitted to GM so the dealer can get paid for doing the update.You need to see the actual TSB number or the Doc Id number of the update they are doing to see what it is trying to fix.

The horn relay is internal to the underhood fuse block. If the wiring checks out and the air bag is good, than the relay may be shorted and keeping the horns on.

What engine do you have? L5P or L96?