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The engine will not crank after replacing the ECM?

Tiny
LARRY1974
  • MEMBER
  • 2007 CHEVROLET TAHOE
  • 145,000 MILES
I bought an ECM for my vehicle one came it was defective, I had already turned in the original one as a core. So, I went and bought a used one which was for a Yukon Denali, however it was no good. I ordered a programmed one using the serial and model number off the used one I bought, it's communicating but when I turn the key it won't turn over.
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Thursday, August 4th, 2022 AT 12:44 PM

10 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,758 POSTS
Hi,

You mentioned you ordered one using the part number from the one purchased that was bad. Is that correct? Or did you use the part number from the original ECM?

I need to know if the present one you have was programmed prior to installing it. The one thing I question is if the antitheft was programmed correctly. I don't know if they can do that off-site.

I attached the directions for reprogramming the theft deterrent module. It has to align with the new module you installed. The last pic is specific to the ECM.

Let me know if you have questions.

Take care,

Joe

See pics below.
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Thursday, August 4th, 2022 AT 8:58 PM
Tiny
LARRY1974
  • MEMBER
  • 6 POSTS
Yes, the computer I bought was programmed. The mechanic who installed it says he did a relearn and it still didn't turn over.
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Tuesday, August 9th, 2022 AT 12:41 PM
Tiny
LARRY1974
  • MEMBER
  • 6 POSTS
Yes, I did get the numbers of the used part that I bought.
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Tuesday, August 9th, 2022 AT 12:45 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,758 POSTS
My only concern is the numbers were different. Is there any way to check the numbers on the old one or was it returned?

Joe
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Tuesday, August 9th, 2022 AT 1:15 PM
Tiny
LARRY1974
  • MEMBER
  • 6 POSTS
Yes, I still have the old one as well. I'll check the numbers now.
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Tuesday, August 9th, 2022 AT 1:57 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,758 POSTS
Hi,

Any luck matching numbers? I'm interested in knowing.

Take care,

Joe
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Thursday, August 11th, 2022 AT 3:13 PM
Tiny
LARRY1974
  • MEMBER
  • 6 POSTS
Yes, I used a scanner to compare the numbers, and the Vin information matches the registration number.
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Thursday, August 11th, 2022 AT 9:41 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,702 POSTS
When you try to crank the engine over does the security light flash? If not, you could have a starter relay that is bad, also can you try to crank it over in neutral and do the gear selector lights work?

This guide may help:

https://www.2carpros.com/articles/starter-not-working-repair

Check out the diagrams (below). Please let us know what happens.
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Friday, August 12th, 2022 AT 10:44 AM
Tiny
LARRY1974
  • MEMBER
  • 6 POSTS
Okay, I took it to the dealership, it was a fuse blown caused by two wires which had to be repaired, however after leaving, it cut off, it started back but was hesitant to idle at first, then it cut off again. It started right back. The truck sat for 6 years, and I've replaced everything, transmission, TCM, ECM, lights, calibers, brakes, rotors and all with exception to a fuel pump. The only code is check engine light on because of evap system. Any idea?
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Tuesday, August 16th, 2022 AT 2:41 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,758 POSTS
Hi,

It sounds like the cranking issue has been resolved. If I understand, the engine won't stay running. Is that correct?

Have you rechecked to see if any codes have returned? Also, do you have a live data scan tool? If you do, I need you to confirm the coolant temperature sensor is accurate. The best time to do this is when it's cold. The ECT should indicate near ambient temperature.

If that is good, then I need you to check what the short-term fuel trims are. We may have a fuel pressure issue. Also, let me know what the evap code is that is stored. You could have a large vacuum leak.

Let me know.

Take care,

Joe
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Tuesday, August 16th, 2022 AT 7:02 PM

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