Pcm ground

[Darrenmb]

I have to be missing something.... new icm and coil, still no spark... think I need to double check my harness, something has to be awry somewhere...

[Injuneer]

Did you measure the AC voltage on the white wire to pin B of the ICM connector, as suggested in previous post?

[Darrenmb]

I did, I get the voltage when spinning opti by hand but cannot see it when ots on motor and using starter, tried with two multimeter, you still thinking its opti??

[Injuneer]

Are you saying that when you reinstalled the Opti, and tested for AC voltage on the white wire to pin B, there was no reading?

If the ICM is not getting that signal on the white wire to fire the coil, you aren't going to have any spark.

[Darrenmb]

That is what I am saying, however, when opti is not installed and spun by hand, i get 8, 4-5 volt spikes on the white wire per revolution and injectors pulse, and fuel pump runs... could it still be opti? Bad wiring? Thing that gets me is motor was running when pulled out of other vehicle... that in itself leads me to think I have something wired wrong.. but everything is per shoeboxes site and lt1 swap.. The opti guy on ebay said I can send it back and he will double check everything. Guess I should do that regardless at this point..

[Injuneer]

Still not clear in my mind.... guess old age is taking it's toll. When you had the Opti off, and spun it, you got the 5V DC pulse at the Opti harness, and injectors pulsed. The proves the Opti is producing the pulses, and the PCM is receiving them.

When you had the Opti off, did you also check the AC voltage on the white wire to the ICM?

At this point, the circuit for the white wire to the ICM is suspect. And you verified the DC volts on ICM connector pins A and D? And you verified the ground on pin C?

Note that the factory service manual, which is what Shoebox shows, shows the ICM pins in the order C - A - D - B. That is not the same order as on the connector, as Shoebox cautions in his writeup.

[Darrenmb]

You are following along well. Lol. I did take note of the acdb thing, noting the letters on the actual connector not the picture.. I will check the wires tonight if I get home early enough, car is still facing out in garage, hood opens backwards creating huge dark area in engine bay, as I have. O lights above the garage door area, oh well, will keep digging and post what I find, thank you for all your help, I swear I am not trying to monopolize your time!

[Darrenmb]

Oops, missed a question in your response, yes I tested white wire and had pulses while opti was off, and yes I checked for ground on c. You can see why I am pulling my hair out here!

[JOATMON]

Just a WAG but I went through all the same tests one time when mine just wouldn't start. After everything tested good I put in a spare coil I had and it fired right up. ????

[Injuneer]

Just a WAG but I went through all the same tests one time when mine just wouldn't start. After everything tested good I put in a spare coil I had and it fired right up. ????

He already swapped out the coil. But maybe the new one is defective.

Can't remember if I already posted this:

http://shbox.com/1/coil_testing.jpg