Cadillac Repair Questions? Ask a Mechanic for Answers ASAP
Welcome, I'm Chris (aka Moose), my normal schedule online is around lunch and after dinner past midnight.
We need to test the powers and grounds for both the EBCM and PCM while cranking. Normally PCM programming update resolves this but you have done that. If you have a volt meter and understand wire testing we can start checking powers and grounds.
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So far you have ruled out all the things that should be to blame, you may need to start redoing these checks and programming. That means the only thing your left with is doing all the pinpoint tests for these codes. Do you have those or need them?
Being they are used modules that could be your issue. After reviewing the diag steps they only state to reprogram the ECM.
Replacing the ECM with a refurbished one and having the dealer reprogram it would be next step since you have confirmed no weak power or ground supply while cranking is present.
You would need to check all these grounds to see if they need cleaning:
The powers also have to be checked to see if power is dropped during and after starting.
Hello again Chris here,