OK, so I have a 383 L31 TPI T56 in an '88 T/A. It previously ran great on the stock ECM with a chip, though it had it's share of driveability problems which led to the swap in the first place. Now after replacing the harness and having the 0411 tuned, it will not run. I get fuel pump prime, even fuel smell and injector pulse while cranking, but no spark. I have:

-verified circuit integrity. All check out ok on the ign circuit.
-verified pinouts according to 02 Express 5.7L schematics. All ok.
-had PCM tuned. When PCM was suspected, replaced PCM again with another tuned PCM. Still no spark
-replaced CMP sensor. No change.
-verified CKP sensor is tight against the reluctor. No excessive gaps. The crank reluctor just barely kissed the tone ring, then was shimmed away .015"
-verified with the tuner both PCM's were VATS disabled
-verified injector pulse while cranking

Problem is I still have no output to the ICM from the PCM. I have CMP and CKP input, but no output. When I used a stock PCM from a 4.3L truck, to verify the circuits before sending in the second PCM, I fired the engine on the stock PCM. It ran (horribly) but it was enough to verify it worked.

Any ideas? I'm hoping to find a way to test the ckp sensor to make sure it's sending a clean and strong signal to the PCM, but with fuel injector pulse, I doubt that's the problem...

if you are SURE the ecm is firing all injectors(also check with a noid light on the end of each injector) if they are indeed firing then your crank sensor is working fine.
but to test the crank position sensor.... remove the sensor from the timing cover and leave wiring pigtail plugged in waive a pocket knife or screw driver back and forth above the sensor and check for rpm on a scan tool.

what harness and year did you use for the swap?
may need to go back and check every single wire for color and correct C1 and C2 location.... I have done 4 0411 swaps and I have accidently pinned one in the wrong hole a few times.... but caught it going back and RE-checking wire color and location.
its something simple I would immagine... also make sure your rotor button inside the distributor is indeed spinning

edit....

also what is your fuel pressure reading in PSI? is this value with FPR hose disconnected match what is loaded in the 0411 or if it doesnt change with a FPR are the values programmed accordingly with the size injectors you are using also?

did you take a timing light and clip the sensing lead to a spark plug wire or even the coil wire and see if it blinks to rule out spark?



Last edited by stroker97k1500 on Sun Dec 25, 2011 11:56 am; edited 1 time in total

I used a couple scrap LT1 harnesses and a scrap thirdgen harness and built a plug and play harness for my '88. I already checked the ignition circuit, will go through and check the rest of the harness for crossed wires that could cause interference.

PCM is firing on all 8 injectors.

Rotor is spinning. I made sure it's phased correctly.

when I made my harness on my truck,the ignition circuit from what I remember, has quite a few splices these are from memory and may be wrong since it was 2 or more years ago.....( a pink/ and black and then a white wire as the IC control. with the coil unplugged and the 0411 ecm connector also, ohm out the few wires bw the C1/C2 connector and the coil/driver and make sure each wire is making the correct path to where it is supposed to go. ( also checking the ignition feed wires into the ecm) then you can plug in C1/C2 on the ecm and check for voltage at the coil

I have system voltage at the pink wire on the coil.

Resistance on the IC timing circuit wire is .0002 ohms. I already checked all the wires on the IGN circuit for shorts, opens, and continuity. All checks out ok as far as power and ground distribution and ign controls.

Also checked the tach signal wire to the coil for an open, even though my problem us between the PCM and ICM, not the ICM and the coil. Checked out good.

Coil terminal B has positive voltage, key on engine off. Even though I suspect the coil because of this (due to the troubleshooter I used), it still doesn't explain the problem on the IC timing circuit. Naturally, swapped back to a stock coil, no change.