'94Z28... same problem I've had. The computer seems to reset, the fuel pump primes, and I think air pump start running, injectors priming.. what I think is everything it first does when you turn on the car.

On the black C210 connector I think it is that one, it has a purple, an orange, a gray, and a blck/wht, not in that order. I disconnected it from the pcm and am looking on the chassis side of it. I disconnected the battery so there's no voltage to mess up the reading and put my multimeter on the negative terminal which is grounded to the chassis so if it's a ground wire I should see ground. I set it to ohms and measured the black/wht wire on the connector. I got 60ohms. I put it on the positive terminal just to see what happens and got ~50ohms. What's up with that? Where does this wire go on the chassis? Is it a ground wire that I should see 0 ohms on it? Is it even something that would affect my car like that? Where does it go on the computer side?

Also, I've checked every power and ground wire on the pcm while it's connected and disconnected and while the problem occurs and I don't seem to get bad readings on anything...except I do get a little voltage drop on the pink ign power feeds when it happens.. it goes from 12 v to about 11.5. I don't know if that's just because of the extra load from the fuel pump priming and whatnot. It happens after the fact though like right after the problem happens so I think it's more or less a result and not a cause. Any input on that too? Maybe the meter is just slow to show it and it's actually at the same time... But would a drop that low be enough to just barely reset or partially reset the computer? And if so how do I fix that? Also, on the main power wires when the problem occurs I don't see any voltage change.

Anyway, it's two weeks later and I'm still stuck without ideas or a car. Any help is appreciated.

 

The blk/white wire brings ground from a splice(s109) which is located about 2 inches from where the harness breaks out to the PCM. The splice is fed with one wire from the ground above the starter. From the splice it goes directly to the PCM, oil level sensor and MAF. The accy's grounded from that splice THRU c210 are DLC, theft deterrent module, tranny position switch, fuel pump relay and the instrument cluster.

If you measured the correct side of C210 to ground with an ohm meter, obviously you should have measured close to 0 ohms. Try both sides. Start there.

 

Thanks for the reply.

I believe it goes to the clear/gray 32 pin on the pcm.. I measured from there to the C210 and got 0 ohms. Then I measured from the c210 on the chassis side of the plug and measured to ground and got about 150 ohms. So maybe something else on that ground circuit is bad? Or does all the interior stuff ground from the exterior connections and won't see zero until plugged into the engine harness?

 

Measure both sides of the connector while it is unplugged from black/white wire to ground. The side that should go to ground should measure close to 0 ohms. The other side will measure who knows what. It doesn't matter. There is no other harness to go through as I mentioned before. If you don't get a reading below 1 ohm, there is a problem. When a connection should be direct to ground, there is no way for a device to be bad and pull the resistance up higher. If it does not measure below 1 ohm, there is a broken or otherwise improper connection.

 

I did and explained the reading I got from each one. I don't know which side is supposed to be zero and which side doesn't matter. Which is the side that should go to ground? Is it the side that goes to the engine compartment or the side inside the car? In other words, does that wire split off to ground on the engine harness side of it or on the interior side of the harness. I'm getting the resistance when I measure inside of the car with the c210 unplugged so that the computer side of it is totally disconnected from what I'm testing. EDIT: Just got back and tested the pcm side with it connected and got 0 to ground. Guess I'm back to where I started.

Also, any input on my car dropping half a volt on the pink ign wires at the pcm when the computer is resetting? Is that just a voltage draw from the increased load or is that a possible cause for the resetting.

It seems like I've checked all the power wires and grounds and they get voltage at the pcm. Is there even anything else that would cause it to act up like that? Maybe the small voltage drop? I'm going to try and test the resistance on those wires. Maybe they just have a bad spot somewhere. This just sucks.. it's 3 weeks now and I'm not any further than I was.

 

Take it to a shop.

 

HAHAH never!

In any event.. I just found the wire. It's the orange wire on the C210 connector interior side. The voltage is jumping all over from 12v to 2 to 9 to zero..Does anyone know where that circuit goes? On my service manual it lists the details for everything but that connector. EDIT: found a vague circuit on the pcm breakdown that shows it going to the instrument cluster and the theft deterrent module then to the fuse box then to the engine bay.

I guess now I'll have to start testing at those various locations.

 

Pretty sure it is a PCM battery feed.