Hey guys,

Im having some trouble with my ignition system. Ive got code 42: electronic spark timing (EST) circuit grounded. The computer isn't controlling the ignition timing because of this. This problem crept up real slow, first it was the occasional misfire then after a couple weeks it would miss going up hills or anything over 1500rpms. Its like a bad wire or something.

Anyways here is what ive done so far:
1. Took 1 year old ignition module to autozone for testing: Passed
2. Checked by pass wire for ground or short: Passed
3. Checked EST wire for ground or short: Passed
4. Checked reference low: Passed
5. Checked reference high: Im not sure, it only had 1Volt. Shouldn't it have 5??
6. Switched out ECM with another

I'm not sure what else to do. Any input would be awesome. Some other info:
16168625 ecm
Accel cap and rotor
msd wires, blaster coil, and 6A controller
TBI 355 mild build

 

I went ahead and ran a whole new EST wire from the module to the computer and I even tried a new module (different brand too) and still no fix..

Heres the strange part. If i disconnect the by pass wire while the motor is running, it runs really rough like it should with no computer controlled timing. I would think it would run no different since its not getting or thinking its not getting timing information from the module.