I recently began having a hard time starting my car. It began very abruptly, with everything perfect one day, then requiring several attempts to start the next day. Ocassionally, the car would stumble at highway speed, feeling like the ignition had stopped firing. I pulled the codes and got the dreaded 16 (loss of Opti Low Resolution Pulse) and 36 (loss of Opti High Resolution pulses).

I checked all the usual suspects, fuel pressure, coil wire resistance, electrical connections, yada yada yada. Nothing. And I could not make the failure occur by wiggling wires, or trying to start it when warmed up versus cold.

The diagnostic charts in the GM Manual for these two fault codes lead you to believe either the Opti Spark or the associated wiring are at fault.

In my case, it was neither. The ignition control module had failed. It controls the firing of the coil. It is located on the front of the engine, on the passenger side head. It is mounted to a heatsink, and has a 4 pin connector that goes to the coil and PCM.

For 74 bucks, my baby is back on the street. I'm not looking at dis-assembly of the front of the engine, removal of the Harmonic balancer, purchasing a new DynaSpark (the best solution if you are not doing the LS1 Conversion), or any of that stuff. I am pleased, to say the least.

I hope this helps others that would be relying largely on the manual for guidance. The bad news is, there was no hard failure or indication that pointed directly to this unit, and I could not find a direct way to test it, since the failure was intermittent.

If others have had this component fail, your observations would be welcome.

:cheers:


[Modified by Da Wiz, 11:54 PM 11/4/2003]