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I have a 96 LT1 I put a painless engine harness on it 2 years ago, I was out with in the jeep and I get to a intersection and it stall, waited a few minutes and it started back up. Went 3 miles and stop at a intersection, and it stalled again. This time it would not start. Found the the bolt on the start came lose. tightened it back up and still no start towed it back to house. thinking the optispark went out, put a new one one and still did not start just turned over and over. So I check to see if I had a signal from the PCM to the ICM, and the is no signal...... there is no blowen fuses, the fuel pump comes on there is a pulse at the intectors as well. What do I look for or what could be my issue with not have a signal from the PCM to the ICM.... any Idea?????

Garycj7
 

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Try having the icm tested at an auto parts store. If it tests good, make them run a bunch of test cycles as icm likes to fail when hot.

The pcm to icm signal is actually from the icm to the pcm. Without this signal, pcm won't tell coil to fire.
 

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If you change icm, don't forget to put heat sink compound on back of icm & on heat sink. Without the compound, icm will burn up quickly.
 

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Discussion Starter #4
ok I am get a signal from the PCM, it is between 1.95 to 2.30 AMPS. new opti-spark still will not start
 

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Proper test of ignition control circuit should be done with multineter set to AC Voltage. Voltage should switch between 1 and 4 volts.
 

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You should consult 96 service manual at following link. It will have full section on ignition. With tests, wiring diagrams, etc.
 

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If you’ve purchased a low budget non GM/ACDelco replacement optispark, there’s a very good chance it’s dead on arrival.
It’s happened a lot more than you can imagine.
The only way to check the opti itself is with an oscilloscope looking for a perfect square wave trigger pattern at the proper voltage levels.
I have the FSM’s on the 96 Impala/Caprice/Roadmaster if you need me to look up a testing procedure and it’s values...
The grease mentioned above on the ICM is absolutely required to keep it from burning up.
 

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Proper test of ignition control circuit should be done with multineter set to AC Voltage. Voltage should switch between 1 and 4 volts.
That information is correct, but you can also have those voltages present, and still not have a properly working optispark.
The trigger sent has to be a close to perfect square wave as seen on an oscilloscope, not a slow rising and falling curve, or it won’t work...
 
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