Programmed new ECM will not start

KWHITE0818

MEMBER
2005 CADILLAC CTS
3.6L
AUTOMATIC
150,000 MILES

Brought my car to dealership to program new ECM, but it still will not start and mechanic cannot figure out why it will not start still.

Tuesday, August 21st, 2018 AT 2:50 PM

5 Replies

KEN L

MASTER CERTIFIED MECHANIC
42,959 POSTS

Can I ask if the security light is flashing?

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Saturday, February 2nd, 2019 AT 1:18 PM

XABROWN22

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2 POSTS

I replaced the ECM as well and my security light is flashing.

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Tuesday, June 4th, 2019 AT 10:53 PM

KEN L

MASTER CERTIFIED MECHANIC
42,959 POSTS

That is the problem then the PCM must not be programmed to the car correctly. I would try to get a replacement coded with the VIN number or tow it to a shop that can do it. Should cost about $130.00. Let me know

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Wednesday, June 5th, 2019 AT 4:10 PM

XABROWN22

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2 POSTS

That still didn't work, the tester doesn't even work on the car.

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Wednesday, June 26th, 2019 AT 10:55 PM

KASEKENNY

MECHANIC
18,907 POSTS

Just to jump in on this, if the PCM will not communicate with the scan tool then the PCM you have is faulty or you have a power or ground issue going to the PCM.

So, we are going to need to start with checking all power and grounds to the PCM. I suspect these will be fine since the engine is cranking so we need to suspect that the PCM you replaced is faulty.

https://www.2carpros.com/articles/how-to-check-wiring

What was the reason you replaced the PCM in the first place? Do you still have the original and can you install it and see if the engine starts?

Let us know what you find. Thanks

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