Contour Enthusiasts Group Archives Forums General Troubleshooting DMD and Check Engine Light

This is just a wild ass guess - but I know the misfire strategy looks at the crank pulses, and it is VERY sensitive to perturbances - so much so that I've read some tranny designs are scrapped because it puts too much noise/vibes onto the crank which causes the misfire monitor to fail.

I'm not sure if it's an adaptive strategy or not, but if it is and it's accoustomed to a signal with "large" amounts of timing scatter coming from undamped harmonics, suddenly removing that scatter could throw of the monitor.

Like I said it's a guess, but reset the PCM anyway, I bet the CEL goes away and doesn't come back......