i just got new heads and cam setup. and i got my computer tuned by bryan at pcmforless. the car ran for 2 days and no big problems.a little rich(my fault) and a small retard from knock sensor(exhaust leaks). now i went out this morning to crank it up and the engine turns over but never fires. the coil is checked out and fine, the plugs are firing correctly, and the fuel injectors are getting voltage on one of the wires.the fuel pressure is 40psi. the computer is throwing dtc 42! DTC42 Ignition Control (IC) circuit (shorted or grounded circuit)
dtc 42 is the white wire going from the Black PCM connector pin 5 to the ICM. This wire is either open or shorted to ground. It should carry a signal that is 1 to 4 Volts AC. i did a continuity test on the wire from connector to connector which is coming up fine. does anyone have any clue as to what i need to check? or anything that i can do to maybe eliminate something else?

ok, so i cut the white wire running from the pcm to the icm. and put in a jump wire. now the car is doing the same thing but now not throwing any trouble codes. im using a scanmaster and i can read all other info, like 02's and everything else but for the trouble codes its just a dash(-) on the display. so i figure that maybe the wire isnt grounding out, and its the pcm. but if there is anything else i can check or you can think of please let me know.

One of the problems with the ScanMaster is that is doesn't have any way of distinguishing between active and stored codes. DTC 42 could have been intermittent.

And, DTC 42 is not limited to problems in the white wire from the PCM. It will also set if the ground circuit for the IC Module is open, or if there is a faulty circuit from the IC Module terminals D or A to the coil, or if the IC Module is faulty, or the ECM is faulty. There is a faily extensive diagnostic logic tree for DTC 42 in the factory manual.

Have you verified that the PCM is supplying ground signals to fire the individual injectors?

yes, all of the injectors are firing correctly.

You say the plugs are firing correctly. How "correct" do you mean? For example at the correct time? You really can't tell if it's at the wrong time unless you eliminate everything else. That is, it's got fuel, got spark and got compression on at least 6. If you have all that, then the only thing left is spark occuring at the wrong time.

Since you see spark and injector pulses and fuel pressure, why don't you check that everything is opening and closing or rotating as it should. At least check compression on 7 or 8 to see if the cam is not broken in 2.

let me rephrase, the injectors are getting a pulse on the positive wire from the pcm. but i have not yet pulled one to see if its actually spraying fuel. my technician put a test bulb on one of the plug wires and it lit up but i cant tell you if it was at the right time. and it didnt seem very bright either. so i went out and bought a new opti and it will be installed tomorrow. but for right now im trying to think and see if its anything else maybe besides the opti.

There should not be a "pulse" on the positive wire at the injector. The pink positive wire comes directly from the fuse box, and should have a constant +12V on it any time the key is on. The PCM fires the injector by supplying the ground via the various colored/striped wires at each injector. You need a 'noid light to see if the injector is firing.

what does this look like, where can i get one and is there any other name for it? the pink wire you say should have a constant 12v. and is that with the ignition in the on position or start?

This is a noid light.
http://www.lislecorp.com/tool_detail.cfm?detail=387
I like this one cause you can jump it in the harness and stick the light portion on the windshield with the suction cup so a "lone" person turning the key can see the pulses from the driver seat. Be careful that the pins are pushed far enough in the back of the injector clip to make contact otherwise you could be a victim of what you think is missing injector pulses.

Several automotive stores carry lisle brand. I got mine from "Snappy".

I also think you could use a test light to see it as well.

One other thing you could do, squirt fuel directly into the intake while someone cranks it over. If you have fuel pressure you pretty much know if starts when you squirt fuel in it but not otherwise, you have missing injector pulses.

thanks, i got a noid light from my roomate who works at an auto part store. i also got a sensor tester to test the camshaft and crankshaft sensor, and ignition module. so im going to see how these come out. then tomorrow morning im going to have the car towed to my installers house so he can put on a brand new opti that i had overnighted.

There are no seperate cam and crank sensors on your vehicle. There are 2 optical sensors built into the distributor. They are hi and low resolution 5 volt square waves and the signals are on the 4 wire harness connected to the opti.

As far as testing the ICM, I seriously doubt it's testable PROPERLY as a stand alone unit.

Hope your opti replacement works.

thanks bro. the opti will be on this afternooon and ill let you all know how its going. i bought an accel which looks bad***, but lets see how it performs.

okay so i got the opti on and its still doing the same thing. as of now i have currently replaced the icm, opti, all of the wires, plugs, checked all of the grounds, checked the theft deterent system, all things like the starter is fine because its actually turning over, the injectors are firing. the only thing left is the wiring harness itself, and the pcm correct? yet im pushing away from the harness because all of the connectors are getting the correct voltage. the other reason i think it might be the computer (pcm) is that i was throwing trouble codes 83 & 84 which are for the transmission, and 42 which is the icm wire. but now its not throwing any and still doing the same thing.

its running. out of all of the things everyone has done to that car to test and replace, it ended up being one of the simplest yet overlooked things. spark plugs were fouled to the point where it wouldnt even crank over, and also i replaced the maf with a bigger one. so either or went bad (spark plugs), and the maf helped lean out my mixture a little. now everything is good to go. and just needs to be tuned out. thanks for all of your help everyone!!!
mike