Mechanics

PCM/ECU

2005 Chevrolet Colorado • 5 cylinder 4WD Automatic •

Vehicle stalls intermitently. Got a P0601 OBDII code, internal memory problem with PCM/ECU.
Got another ECU from salvage yard. They said if it was a certain serial number it would
not need to be flashed. I gave them the serial number on mine they sent me one they said
matched and would not need to be flashed. When I put theirs in, the truck would not start
(or fire). The engine would crank but not fire. Any thoughts? Any help will be appreciated
Avatar
Rwilley1
April 30, 2011.




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's 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're running leaving you stranded somewhere. Many other brands fail to start up but once they're running, they continue to do so until the engine is stopped.

Caradiodoc
Apr 30, 2011.
Did you do a Passlock relearn?

30 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 10 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 Passlock Sensor Data Code and/or passwords on the next ignition switch transition from OFF to CRANK).
Important
The vehicle learns the Passlock 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 Passlock Sensor Data Code and/or password).
7. With a scan tool, clear any DTCs if desired (history DTCs will self clear after 100 ignition cycles).

Wrenchtech
Apr 30, 2011.
Wrenchtech,
No, I have not done a passlock relearn (didn't even know it existed) but will give it a shot. Thanks.

Caradiodoc,
Agree with your assessment of the car mfg "gotcha's". I had no idea they could or would lock all the computers together. Guess I'm just a naive old man.

Thanks to both for your replies.

Ralph

Tiny
Rwilley1
May 1, 2011.
The VIN# is part of the programming for most modules in most vehicles these days.
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Wrenchtech
May 1, 2011.
You're 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 weren't 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's 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 30 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 30 computer modules were replaced and it took two days to install the software into them one at a time. With a second one, he didn't 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's how we know we can believe what he tells us.

My biggest problem is I can't remember everything he says because I miss so much while I'm feverishly writing notes. In your case, I'm very interested to hear why the salvage yard asked about the serial number. That implies Wrenchtech's procedure for simply programming the Passlock code is all that's 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 won't change that but it will sure be better for the owners.

Caradiodoc
May 1, 2011.
I can't tell you if the relearn is the only problem but I can positively tell you that it won't run until the relearn is done.

Wrenchtech
May 1, 2011.
Put the ECM in from the salvage yard and did the relearn procedure yesterday and the truck started right up. Now a few days of driving will tell if the ECM fixed the original problem.
I really appreciate the help. If it weren't for Wrenchtech's relearn procedure I would be tearing my hair out (what there is left) and spending more money. Thanks Wrenchtech.
Regarding why the salvage yard was interested in serial numbers. He said that certain serial numbers will work as a replacement without having to be reflashed (which costs about $150 here, outside Atlanta, GA. So, I gave him the serial number, VIN # and all the information about the vehicle so he could match them.
Thanks Again.

Tiny
Rwilley1
May 2, 2011.
Glad to hear it worked out for you.

Wrenchtech
May 2, 2011.
Me too. Gonna 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.

Caradiodoc
May 2, 2011.
Latest and hopefully last feedback on this issue. The truck is and has been running fine the last 4 days, so I am assuming changing the ECM and relearning the passlock procedure fixed the problem. Thanks again for the help - could not have done it without help.

Ralph

Tiny
Rwilley1
May 4, 2011.

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