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International Automotive Technicians Network
Re: GM REF HI and EST issue
Posted to Technical Discussion Forum on 10/26/2023

Did you by chance do a current ramp on the ignition coil? I have had ignition coils with shorted windings cause erratic ignition module behavior. I know it runs fine the rest of the day, but it may be that the coil get warmed internally and no longer presents ... Login to read more.