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I did an intake manifold on my '94. Now it won't start.
Got code 16, and 42. 42 basically means it cranked for 94 revolutions without spark.
(I also get code 43 for both knock sensors, but I'm not sure if that's normal when not running)
Just to be safe, I replaced the ICM and coil, cleaned the heatsink, applied new thermal paste, etc.
I had a code 16 before when it was running and driving, so that's not a 'new' symptom, but it won't start, and I verified the coil is not firing.
The easy thing to try is a new opti harness, and change the coil connectors/pigtails (they do look bad).
Is there an easy on-vehicle optispark test? I googled for a procedure and couldn't find one. Everyone is ohming out the harness, and I get that, but I'll just install a new harness. How do you test the signals from the opti itself?
Opti was replaced in 2015 by previous owner, along with a new water pump.
With key on, At the ecm side of the connector where the opti harness connects, check for 5Vdc between the yellow wire (ground) and the black/pink wire (signal feed). If there is 5 volts there then repeat at the end of the harness that connects to opti sensor. If no 5 volts is supplied by the ECM trace the wire to ECM connector C9 and C18.
If 5 volts is supplied to opti and no signal is being seen then the opti sensor may be out.
Verifiying an opti signal takes an oscilloscope and ive never done that...
If you just did the intake and it was fine before it's hard not to suspect a simple connection issue.
I will get some pictures of code 16 flow chart from a 92 FSM but that won't be until late tonight. Hopefully if I've misspoke on this someone will correct me. Good luck
Last edited by AJT84; May 28, 2017 at 03:27 PM.
Reason: Missing detail
With key on, At the ecm side of the connector where the opti harness connects, check for 5Vdc between the yellow wire (ground) and the black/pink wire (signal feed). If there is 5 volts there then repeat at the end of the harness that connects to opti sensor. If no 5 volts is supplied by the ECM trace the wire to ECM connector C9 and C18.
If 5 volts is supplied to opti and no signal is being seen then the opti sensor may be out.
Verifiying an opti signal takes an oscilloscope and ive never done that...
If you just did the intake and it was fine before it's hard not to suspect a simple connection issue.
I will get some pictures of code 16 flow chart from a 92 FSM but that won't be until late tonight. Hopefully if I've misspoke on this someone will correct me. Good luck
I changed the opti harness, still no start.
I've got a FSM for my '94. I guess I'll follow the troubleshooting chart.
I do have a scope.
Thanks for the suggestions. I do have a brand new opti in a box in the shop, I wonder if I should just change it. Can't be more than a few hours lol.
Optispark or harness problem
