Bad PCM/ECU?

GM has figured out yet another way to separate you from your money and that is by building computers that will not work in any other vehicle. You must buy a replacement from the dealer and have it programmed to your car. Got'cha! They started this nonsense with the 2002 models.

Also, you should be aware that when a mechanic has a scanner connected to your truck, he has the choice to press the "lock" button. You will never know that was done but it ties every computer on the truck electrically to the Body Computer which, to prevent you from replacing it, is built into the radio. No clue how this benefits the owner but it is a real good deal for GM. Once that is done, they can not be unlocked. If the high-failure radio needs to be replaced, you must also replace every other computer on the truck. Imagine, a truck that is not worth repair because the radio failed. This is just one of many reasons GM has lost so many of their repeat customers.

The safest thing you can do is to reinstall your old computer and take it to the dealer so they are responsible for anything that stops working. Most likely no one ever locked the computers so all you will need is the one Engine Computer, but I would have them do the diagnostic tests first and come up with their own conclusion. There are a number of more common things that cause stalling. In particular, GM fuel pumps often quit while they are running leaving you stranded somewhere. Many other brands fail to start up but once they are running, they continue to do so until the engine is stopped.

Did you do a Passlock relearn?

Thirty minute re-learn procedure:
1. Turn "on" the ignition, with the engine "off".
2. Attempt to start the engine, then release the key to "on" (vehicle will not start).
3. Observe the security telltale, after approximately ten minutes the telltale will turn "off".
4. Turn "off" the ignition, and wait 5 seconds.
5. Repeat steps 1 through 4 two more times for a total of 3 cycles/30 minutes ( the vehicle is now ready to relearn the Pass-lockâ Sensor Data Code and/or passwords on the next ignition switch transition from off to crank).
Important
The vehicle learns the Passlockâ Sensor Data Code and/or password on the next ignition switch transition from off to crank. You must turn the ignition off before attempting to start the vehicle.
6. Start the engine (the vehicle has now learned the Passlockâ Sensor Data Code and/or password).
7. With a scan tool, clear any DTCs if desired (history DTCs will self clear after one hundred ignition cycles).

The VIN numberis part of the programming for most modules in most vehicles these days.

You are not a naive old man. We expect manufacturers to have our best interest at heart and work to earn our repeat business. I worked for two TV repair shops many years ago. One fellow's motto was he had had to rip off the customer as much as possible the first time because they were not coming back a second time. He went out-of-business for lack of customers in an extended community of well over 100,000 people. That is the business practice of GM and Volkswagen.

My cousin made a nice living for him, his sister, and me on weekends in his tiny repair shop in a farming community of 2,000 people. He never had to advertise. All of his work came from word-of-mouth. He only quit business after thirty years because of failing eye sight and increasing taxes.

As far as locking the computers, we were warned about that numerous times by a very high-level Carquest trainer who ran into that on more than one occasion. In at least one of those the car was still under warranty so GM got to eat that one. We were told more than thirty computer modules were replaced and it took two days to install the software into them one at a time. With a second one, he did not know what the final outcome was after the customer towed it back home. This instructor owns a shop that specializes in driveability problems that no one else can figure out. Most of his customers are other shops. He is part of a network of similar shops and instructors all over the country and they are in constant contact with the engineers at the manufacturers. That is how we know we can believe what he tells us.

My biggest problem is I cannot remember everything he says because I miss so much while I am feverishly writing notes. In your case, I am very interested to hear why the salvage yard asked about the serial number. That implies Wrenchtech's procedure for simply programming the Pass-lock code is all that is needed. In spite of my sarcasm and disgust, I will be very happy to learn if that works. I have enough disdain for all of the unnecessary, unreliable computers on cars already. One less thing to be miffed over will not change that but it will sure be better for the owners.

I cannot tell you if the relearn is the only problem, but I can positively tell you that it will not run until the relearn is done.

Glad to hear it worked out for you.

Me too. Going to have to add that to my internal memory.

As a side note, I visited about a dozen Pull-A-Part salvage yards a couple of years ago including three in Atlanta. Met a lot of friendly people down there all over the place.

Hello,

Thanks for the compliment we do try to be a step above. Yes, it does sounds like you have a computer problem and I would go ahead and try the PCM you found on Ebay.

I would clear the codes and see if the car does it again first it could have been a voltage serge or a glitch.

Please let us know what happens.

Cheers, Ken

Please let us know what happens.

Cheers, Ken

If the security light is not flashing the pass lock is okay. Do you have spark and fuel pressure?

Here is a guide to help:

https://www.2carpros.com/articles/car-cranks-but-wont-start

Please let us know what happens.

Cheers, Ken

Lets pull all of the spark plugs out to see if one looks different than the rest and lets do a compression test.

https://www.2carpros.com/articles/how-to-test-engine-compression

Look for one low cylinder.

Please let us know what happens.

Cheers, Ken