Chevy Impala SS Forum banner

New opti?

353 Views 9 Replies 7 Participants Last post by  sherlock9c1
I have a 95 caprice has been treating me well for about 2 years until today on the highway the engine just shut off and wouldnt restart. First I checked fuel pressure had 40+ psi, checked for spark at the wires then coil, none. Checked all fuses and grounds. I found some info on testing for voltage and resistance on the opti and icm connectors and the ac signal to the ICM. Everything was good except I had 0 AC voltage going to the ICM on pin b when cranking. I traced the white wire back to the ECM, back probed and still 0 when cranking. Should I buy a new opti? I don’t have a scanner or a scope so I’m limited on testing but from what I’ve read it seems mine failed. Any suggestions?
1 - 10 of 10 Posts
Before you say Opti-, several ignition components are cheaper and easier to replace than the Opti-.
Coil, Driver Module, Opti- electrical harness, Vent & Vacuum Harness.
They tend to get overlooked.
Based on your failure mode, my GUESS is Driver Module or Opti- electrical harness.
If someone smarter or more experienced than I chimes in, take their advice instead.
  • Like
Reactions: 2
Well it was the ICM and yea for sure I do need a scanner
  • Like
Reactions: 2
My $ was on the coil. When I had a no start issue not long ago that was the culprit. It was an MSD. People on the forum say to avoid that brand, at least for the coil (I learned after the failure). Their plug wires and ignition box have been working great for many miles now. How did you determine it was the ICM if the voltage was good? Thanks for reporting your fix for the problem child. 😁 Selfishly, I'm always interested how people solve their car issues as it'll probably happen to mine too, sooner or later. In addition, it's good for the forum.
I always recommend a known good coil/ICM mounted on a bracket.
Narrows down ignition issue(s) with quickness.
  • Like
Reactions: 1
What's a good brand coil for the 96 Impala? I put in a Duralast.
+1 on AC Delco and ICM
first off, only fools suggest the opti as a first culprit. Especially without any diagnosis. literally the hardest part of the ignition system to replace.

If you got no AC signal on the white wire while cranking, that could be because at 400 RPM crank speed, a V8 will only be putting 26hz on that wire. The filters on the voltmeter are set for 60 Hz and may filter that out. Better to use a test light on that wire.

It is possible that the ICM could have shorted that wire, but you would have gotten a code 42. The PCM does check resistance on that wire, whether above or below a threshold, and it will throw a code for each error condition.
1 - 10 of 10 Posts