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Discussion Starter #1
ECM Replacement

Gentlemen:
I have 2005 CTS with 272,000 miles. Car has been diagnosed as needing new ECM.

I do not have the money to buy from dealer or buy from third party and have reprogrammed.

If I buy a used ECM from a junk yard that comes off an IDEDNTICAL CTS, and replace my
defective with the used part, as is - no reprogramming, no VIN #, nothing. --- will the car start, run?

Just trying to keep it alive.

Joe
 

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Re: ECM Replacement

Each PCM should be programmed for the car it was originally installed in -​ Buy a used PCM, it can be reflashed to your car's VIN.

You could try the used junkyard PCM - but I don't give it much hope. A reflash should be pretty inexpensive at a decent Mom&Pop shop that has a GM internet link.
 

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Re: ECM Replacement

it will definitely work but it wont match ur cars vin # . i have a junkyard ecm on my cts for almost a year now and never had an issue
 

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Discussion Starter #4
Re: ECM Replacement

Thanks, I want to try it. Live in Jacksonville area. Got any ideas on what I should ask for? Joe
 

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Discussion Starter #6
2005 CTS
My ECM is a #12592124.
I bought a good #19260507 thinking it would work. Car would not crank but key came out of ignition just fine where it would
not with the #12592124.

Can I get the #19260507 reprogrammed to be a #12592124? It came off an identical CTS.

If not, I have a perfectly good #19260507 for sale.
Regards,
Joe
 

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Yes, you can. You need to get the new ECM reprogrammed to your VIN.

I believe the #19260507 is just AC Delco's part number, but I could be wrong.
 

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Hey guys, Just following up on this old thread.

I have a 2005 CTS that just developed an ECM problem. The car runs, but the ECM doesn't fire injector #1 any more.

Note that 12592124 is the hardware PN and the 4 letter code on the ECM is the software code. Think of it as a software version designation.

For instance, mine is PN 12600547 YLTT (service no: 12592124).

The YLTT is the software designation. I got this information straight from the parts department of our local Cadillac dealership.
 

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Another follow up... I installed a junkyard ECM and it disabled my ability to start the car. I guess I will have to get it flashed at the dealership. All PNs match up, including the YLTT software code. The only difference is that it is from a SRX instead of a CTS. Can anyone tell me if there's a key cycle pattern to go through to get the car to accept the new ECM?

EDIT: Never mind, I found a GM Passkey key relearn sequence.
 

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Did this work for you after the key relearn sequence? You never had it programmed to your car? Trying to decide how to fix my bad ECM on 2005 Cadi CTS 3.6. Shop wants 1400. I see them online coming programmed to your VIN for $350.

many thanks!

Another follow up... I installed a junkyard ECM and it disabled my ability to start the car. I guess I will have to get it flashed at the dealership. All PNs match up, including the YLTT software code. The only difference is that it is from a SRX instead of a CTS. Can anyone tell me if there's a key cycle pattern to go through to get the car to accept the new ECM?

EDIT: Never mind, I found a GM Passkey key relearn sequence.
 

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Did this work for you after the key relearn sequence? You never had it programmed to your car? Trying to decide how to fix my bad ECM on 2005 Cadi CTS 3.6. Shop wants 1400. I see them online coming programmed to your VIN for $350.

many thanks!
You will find that after you replace the ECM, there is a key relearn sequence. No matter if the ECM matches your VIN or not. On my car, the "new" ECM does not match the VIN of the car and it works fine.

The dealer would have to do the same key relearn sequence. It's easy and takes only 30 minutes.

See the attached PDF file.
 

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You will find that after you replace the ECM, there is a key relearn sequence. No matter if the ECM matches your VIN or not. On my car, the "new" ECM does not match the VIN of the car and it works fine.

The dealer would have to do the same key relearn sequence. It's easy and takes only 30 minutes.

See the attached PDF file.
Thanks for the reply and for the PDF. I was more asking about whether the ECM had to be flashed/programmed. From your post, it looks like you pulled it out of a junkyard vehicle and put it straight in your car without flashing/programming it (separate from the key relearn sequence). Going to try this this weekend - will be a lifesaver if it works. Thanks again for the response.
 

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Thanks for the reply and for the PDF. I was more asking about whether the ECM had to be flashed/programmed. From your post, it looks like you pulled it out of a junkyard vehicle and put it straight in your car without flashing/programming it (separate from the key relearn sequence). Going to try this this weekend - will be a lifesaver if it works. Thanks again for the response.
Correct. Just match the part number and software code. For instance, mine was PN 12600547 YLTT (service no: 12592124) . I installed it without re-flashing. From my limited understanding, all the dealer would change is the VIN stored in the ECM anyway. I believe this mismatched VIN is what will cause the security system to reject the key. So the "new" ECM needs only the key relearn sequence to have it accept the new keys.:)
 

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Correct. Just match the part number and software code. For instance, mine was PN 12600547 YLTT (service no: 12592124) . I installed it without re-flashing. From my limited understanding, all the dealer would change is the VIN stored in the ECM anyway. I believe this mismatched VIN is what will cause the security system to reject the key. So the "new" ECM needs only the key relearn sequence to have it accept the new keys.:)
Had my CTS towed from shop to office today to get it out of the shop and so I can try the ECM install this weekend. When tow driver dropped it off, I got in and it cranked right up... still throwing P700 code... but weird, and frustrating...

Separately, and the reason I came to post, was the tow driver and I talked about the ECM and he said his brother owns an inspection station/shop, and had inspected a car recently with a replaced computer pulled from a junkyard, and that because the VIN stored in the ECM did not match the car, it was not supposed to pass inspection... his brother passed the car anyway but 2 days later was arrested, charged with 2 felonies, and JAILED for passing the car. He believes DMV was tipped off after the customer was pulled over, had illegal window tint, police seeing the paperwork from the inspection from the day before and referring DMV to the inspection station, who then saw in their system that the car was passed despite having mismatched VINS on ECM and car. There may be more to the story as it seems hard to believe he would be charged with two felonies even if it is true he was not supposed to pass due to mismatched VINS.

Anyway... the point is, he told me if I did not get it flashed/programmed to match my car's VIN that I could expect problems when my inspection was due. Dont know whether that is true but just thought I would pass that story along.. for the record I am in NC and DMV is known to be targeting inspection stations for passing vehicles they are not supposed to.
 

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Had my CTS towed from shop to office today to get it out of the shop and so I can try the ECM install this weekend. When tow driver dropped it off, I got in and it cranked right up... still throwing P700 code... but weird, and frustrating...

Separately, and the reason I came to post, was the tow driver and I talked about the ECM and he said his brother owns an inspection station/shop, and had inspected a car recently with a replaced computer pulled from a junkyard, and that because the VIN stored in the ECM did not match the car, it was not supposed to pass inspection... his brother passed the car anyway but 2 days later was arrested, charged with 2 felonies, and JAILED for passing the car. He believes DMV was tipped off after the customer was pulled over, had illegal window tint, police seeing the paperwork from the inspection from the day before and referring DMV to the inspection station, who then saw in their system that the car was passed despite having mismatched VINS on ECM and car. There may be more to the story as it seems hard to believe he would be charged with two felonies even if it is true he was not supposed to pass due to mismatched VINS.

Anyway... the point is, he told me if I did not get it flashed/programmed to match my car's VIN that I could expect problems when my inspection was due. Dont know whether that is true but just thought I would pass that story along.. for the record I am in NC and DMV is known to be targeting inspection stations for passing vehicles they are not supposed to.
That sounds legit in states where inspections are done. Mismatched VINs are often viewed as stolen vehicles. That was probably the angle the state was coming from. I live in Illinois (ugh) and they do not have auto inspections... at least not in the city I live in. Chicago may be another story. They tend to do their own thing no matter what the rest of the state is doing. So getting the VIN flashed on the ECM sounds like the safe thing for you to do.
 

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update on my end. installed ECM pulled from junkyard. when i turn the key to 'on' to begin the key relearn sequence, the security light does not stay on. however, the T/C light stays on which is new. I tried to go through the key relearn sequence anyway but am unable to turn the key back to 'off' due to the theft deterrent system i guess. i tried to go through the key relearn sequence just turning it back to 'acc' in between the 10 min 'on' position, but that did not work. my thoughts are either the ECM from the junkyard is also bad, or the ECM is not the problem. Any additional thoughts or suggestions would be appreciated.
 

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No idea. I've never heard of or dealt with an issue like this. Maybe disconnect the battery for a day, then retry.
 

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Under the steering wheel pad are 2 holes, you will need to stick a object inside of one of the holes to release the key. Use the forum search feature for this procedure. My hat is off to the person that was able to get a junk yard ecm to work without it being programmed to his car. As for myself I would at least go the route of ordering a refurbished programmed plug and pay ecm from a vendor if not going new. Check on Ebay. The frustration can be overwhelming going any other route..
 
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