How to replace the ECM (PCM)

Tiny
CHABUNGA
  • 2002 CHEVROLET TRAILBLAZER

Six cylinder four wheel drive automatic 84,000 miles.

How do I replace the ECM? I am not even sure where it is. What do I replace it with? I have seen where I can buy reprogrammed ECM's. But I have also been told I have to have it programmed after install. Thanks in advance.

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Saturday, November 28th, 2009 AT 8:52 AM

15 Replies

Tiny
RACEFAN966
  • EXPERT
  • 5,126 POSTS

It is not to hard to do. First disconnect the battery positive cable first (and when putting battery cables back on put positive back on last). Now find the PCM it is on the intake plenum front part on the left (drivers) side of the engine. Now remove the bolts that hold the wiring harness on to it and unplug them then loosen the four bolts that hold the computer onto the intake and remove it. Replace in reverse order. Now you must take the truck to the dealer to be programmed to you truck. There are no pre-programmed computers for you truck as it needs to be flashed to you truck according to your VIN number. I must ask why are you replacing the computer?

Here is a picture of the computer and one of how it is mounted on the intake:

Computer


http://www.2carpros.com/forum/automotive_pictures/249564_296254_1.jpg



How it is attached


http://www.2carpros.com/forum/automotive_pictures/249564_Graphic_156.jpg

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Saturday, November 28th, 2009 AT 9:03 AM
Tiny
CHABUNGA
  • MEMBER

The "service engine soon" light has been coming on and one time we had a light come on that said something about reduced engine performance. I went to Autozone and they ran a scan when the "service engine soon" light was on. The code was P0601. They said the ECM needed to be replaced. They are telling me if I supply VIN number, year, make, model, engine size, OEM number of ECM I will receive correct flash computer. Flash technology unit pre-programmed at the factory.

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Saturday, November 28th, 2009 AT 9:19 AM
Tiny
RACEFAN966
  • EXPERT
  • 5,126 POSTS

This has to do with PCM memory. What is recommended before replacing it is to have it cleared and see if the code comes back. If it does then replacement is needed. With all the proper information year make model VIN number then yes you can get a reprogrammed PCM. I have seen a bad battery cause this as well.

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Monday, November 30th, 2009 AT 8:18 PM
Tiny
CHEVYGIP
  • 2002 CHEVROLET TRAILBLAZER
  • 91,000 MILES

I bought a used computer for this 2002 trail blazer. What has to be done to get on an running. Does it need to be reprogrammed.

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Saturday, November 18th, 2017 AT 9:28 PM (Merged)
Tiny
CARADIODOC
  • EXPERT
  • 28,976 POSTS

You're right in the middle of when they went to that nonsense of preventing you from buying an inexpensive used computer. Regardless of whether it has to be programmed to your truck, it's going to have to be installed, so you might as well try it. If the truck will still run with the old computer, you might want to install the replacement in the dealer's parking lot. They don't do anything for free but at least if it does need to be programmed by them, you won't need a tow truck.

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Saturday, November 18th, 2017 AT 9:28 PM (Merged)
Tiny
JDCALDWELL
  • 2002 CHEVROLET TRAILBLAZER

Electrical problem
2002 Chevy Trailblazer 6 cyl Four Wheel Drive Automatic 107000 miles

I have been trying to install a bypass module in my trailblazer so I can install my new remote start. The module requires me to dial in the corrrect resistance value from the pass wire off ignition swith. With my digital ohm meter I am getting an alternating resistance variable exerytime I turn the key to crank. My question is how can I get a specific variable that will stop me from tripping my security and leaving me stranded for ten mins? Or should I buy an auto learn bypass module? Wont the alternating resistance be hard for even an auto learn bypass to zero in on? I found that hooking up the remote start not as hard as I have heard, just the bypass that has me stumped. Thanks a heap for your input! JD

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Saturday, November 18th, 2017 AT 9:28 PM (Merged)
Tiny
JDCALDWELL
  • MEMBER

Thanks for your input. I have an auto learn bypass enroute. Hope that does the trick. Bulldogsecurity. Com also has a complete accurate wiring diagram for any vehichle for future info.
JD :lol:

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Saturday, November 18th, 2017 AT 9:28 PM (Merged)
Tiny
TAPIA213
  • 2004 CHEVROLET TRAILBLAZER
  • 6 CYL

Replace ecu 04 trailblazer

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Saturday, November 18th, 2017 AT 9:28 PM (Merged)
Tiny
WRENCHTECH
  • EXPERT
  • 20,907 POSTS

Are you asking how to? This is something that needs to be done by the dealer because it has to be programmed after it's installed before it will run.

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Saturday, November 18th, 2017 AT 9:29 PM (Merged)
Tiny
JZAL1987
  • 2004 CHEVROLET TRAILBLAZER
  • 103,000 MILES

My wife was driving home from work yesterday and said the truck was running very rough. While she was stopped at an intersection, it stalled out. She figured it was because she was low on fuel so she stopped and put about 8 gallons in. The fuel gage did not move at all and she noticed that the oil pressure gage was pegged out over 80 psi. She was able to drive it to me at work and I gave her my car. After work, I tried to start the truck and it did not even attempt to turn over. Slight click heard from the starter, gauges lit up, engine light came on. I turned the key back to the ACC position and could hear an eerie noise from what seemed like behind the radio. I tried to start it again and the same thing happened. When I tried to remove the key from the ignition, it would not release or turn all the way to the off position. Also tried to shift gears with no luck either. I disconnected the battery and the truck is just sitting right now. I am pretty sure that it is an issue with the ECM, BCM, or Car Gods forbid, BOTH! Any insight or suggestions would be much appreciated since these are both very expensive parts and the timing on this could not be any worse(my wife is 8 months pregnant with our first child). I did just replace the trans oil cooler lines on this wonderful vehicle no more than two weeks ago. Changed the oil at the same time and all fluids were added to vehicle specs as well as checked periodically for about a week after. Thanks in advance!

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Saturday, November 18th, 2017 AT 9:29 PM (Merged)
Tiny
TY ANDERSON
  • EXPERT
  • 705 POSTS

It sound like you may have an issue with your charging system. Try jump starting the vehicle and see how everything works ( rough running, oil pressure). Low voltage can cause electronics to behave erratic. Check the battery terminals for any corrosion and that the clamps are tight on the battery. You should not be able to move the camps by hand. Try this and get back to me. TY

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Saturday, November 18th, 2017 AT 9:29 PM (Merged)
Tiny
JZAL1987
  • MEMBER

I will try that tomorrow morning and let you know how it goes. Thank you for that extremely fast response!

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Saturday, November 18th, 2017 AT 9:29 PM (Merged)
Tiny
TY ANDERSON
  • EXPERT
  • 705 POSTS

Sounds good let me know

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Saturday, November 18th, 2017 AT 9:29 PM (Merged)
Tiny
JZAL1987
  • MEMBER

It turned out being the alternator. It went haywire and fried the battery and took out about 10 fuses. Luckily the batter was still covered under the warranty by 3 months! Replaced the alternator, battery, and bad fuses and it is running great. Thanks for the help!

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Saturday, November 18th, 2017 AT 9:29 PM (Merged)
Tiny
TY ANDERSON
  • EXPERT
  • 705 POSTS

Good to hear! Nothing too serious.

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Saturday, November 18th, 2017 AT 9:29 PM (Merged)

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