I am doing a swap with a Duramax 08 LMM, when I try to read the ECM with ether EFILive or my scan tool I get a failure, the engine seems to be running OK but I have a MIL light and would of course like to be able to work this out.
I have another 08 LMM in the yard and both EFILive and the scan tool work fine on that vehicle. I am assuming there is a problem with the stand alone harness but would welcome any input, I get the same failure when trying to read the TCM

I did not have EFILive when I test ran the engine before pulling it.