Daniel6718

i unbolted it for the timing cover but didnt remove the wires just let it hang and put it back on

Diplomat

Sorry dude, your opti unit is toast! these thing are soo sensitive, I can't say enough when taking these engines apart or working on them to be careful and treat this thing like its a new born baby!

In the back of it there is a little slot, before you junk it check that you installed it right. There is a peg that needs to slide in all the way...not sure if you ever had a pleasure of working on a auto transmission. Its the same when installing the torque converter, yeah it slides in and mounts up but unless you feel that last click its going to blow on ya.

Diplomat

here is cut out from GM Hight Tech Magazine:

"Almost simultaneous with the installation of our BMR suspension last fall, we experienced a failure of the Optispark unit. We quickly ordered this new one from GM Parts Direct, which arrived damaged. A week later a replacement was received and installed by reader Rich Trepczynski of Warren, Michigan. This set us back time-wise, and a follow-up drag test was impossible for the remainder of 2002"

Chevy Performance Magazine:

"The LT1 is a great engine, but the Optispark distributor gives it a bad rap, for obvious reasons. It is pretty unbelievable how fragile this thing is, especially in its non-vented form (93-94 F-Bodies). Driving in heavy rain, going through a car wash that sprays the underbody, these are all events you should avoid like the plague if you want to keep your F-body running right.

That said, the #1 reason Optisparks take a dump is from the water pump, which is haphazardly located right above it, leaking onto it, #2 is stress or heavy road conditions which shake it to death #3 is installing or removing the unit.

I replaced mine after my water pump had a leak, I attempted to do it myself but at the end found myself spending twice the amount of money than I should have. First optispark was damaged by FedEx. Box arrived clean and free of any damage but it was not firing. I called and received the replacement part. After I though that I installed the unit correctly yet again I had no ignition. After spending numerous hours on the phone with tech support I was told that I did not install the unit correctly and damaged the unit again. I end up shelling out another $500 for another brand new distributor shortly after."

Daniel6718

besides opti bashing...back to the experts

is the icm white wire when cranking always supposed to have 1-4 volts AC? and where does that 1-4 volts AC come from

Injuneer

Since you left the Opti hanging by the harness, have you checked the harness connector to insure it is not loose, the clip is not broken, the pins are not corroded or damaged? Apparently you managed to pull a wire out of the harness. How did you repair it? Don't forget to check the other end of the harness on the side of the intake manifold.

Guest47904

The IC signal comes from the PCM. It determines when to signal the ICM to fire the coil based on the feedback from the opti. The opti tells the PCM where it is in the ignition cycle.

That being said, if you dropped the low res signal from the opti, it would have a code but would NOT light the SES.

Daniel6718

ill scan it again...the opti plug was removed only the plug wires were left on the opti...he wire that pulled out of it simple pulled out of the connector in 1 piece...i had to bend the clip on the end of it that holds it into the platic at the end...its fixed...

Daniel6718

ive checked the wires on the side of the intake...

Daniel6718

any other help injuneer shoebox speedy? just got done checking and definately no codes

Guest47904

Probe the hi res and low res signal lines while they are connected and power is on to see if they change from 0 to 5 volts DC while slowly rotating the engine over by hand. Obviously it's going to be easier with the plugs out but your choice.

Daniel6718

will do...get back with your shortly...is it a sware wave? and is it ac? and what wires exactly?

Injuneer

It is a DC voltage, varying between 0V - 5V, in the form of a square wave. It is measured with a DC volt scale. High res signal (360 equal length pulses/cam revolution) is on wire 430 (purple/white or lt blue/black) to pin B20 on the PCM. Low res signal (8 variable length pulses/cam revolution) is on wire 453 (red/black) to pin B2 of the PCM. Measure frmo the signal wire to the pink/black wire to pin B3 on the PCM.

Daniel6718

i got it figured out guys...the opti harness was repaired i suppose at one time and the harness was built backwards...abcd on the opti wasn dcba instead...so when i plugged it back in on the side of the intake i plugged it in right and the wouldent fire...whoever did this before fixed their mistake by plugging the side of the intake in backwards...so i copied them and all is good...

i firugred this out by checking the injectors and they had 12v at the non pink wire all the time...then went to look at the opti and it had everything mixed up...thanks for the help guys...

Guest47904

If the scanner was working, you would have found it a while back. You need to figure out why it's not working with a known failure.

Injuneer

Ditto.... this problem was obvious from your initial post.