4th Gen 4 Life

Ok so I will start from the top of all the test I have done. First thing is I done my multimeter test on my ICM and and optispark/PCM. The ICM checked out good except for the firing signal from the PCM. The optispark on the other hand read(key on)

A .325 VDC
B .325 VDC
C 12.00 VDC
D 111.6 OHMS

Well it seems on not getting response from the PCM.

Ok the first thing the car done before the no firing issue started was when I turned the key it was kinda stiff but went on forward with little effort. So I tore into the column tearing the steering wheel down only to find out the ignition switch is actually halfway down the column. Anyways I got to the switch and found it was wore out and shorted out and burn two wires(two pink) on the switch plug. So I had a parts car and robbed the ignition switch plugged it in and it still does not fire. All my fuses are good(didn't check fusable links)?.
Seems Im not getting any response from the.PCM at all? Also I have swapped the PCM with another and still nothing? Any help would be a life saver. Here's a pic of the switch..

GaryDoug

Those readings are indicating you are not getting the 5vdc from the pcm to the distributor (pins A and B). Do you hear the fuel pump prime for 2 seconds when you switch on the ignition? If not, you may have lost the 12v power feed to the pcm. Check the 15-amp #5 fuse in the inside fuse panel. If you don't have 12v at that fuse with the ignition switch on, the switch wiring or connector may be defective. It is the pink wires that go to the pcm.

Injuneer

How did you determine there is "no response from the PCM at all"? Did you try scanning it?

I've always been under the impression that the module in the Opti produces the 0-5V pulse signal, and the Opti accepts it. I wasn't aware the PCM supplies a 5V reference, and the module pulls it down to 0V to create the pulse. Learn something new every day.

4th Gen 4 Life

Now that I think about it Gary I have not heard the fuel pump. I will double check today. Fred Im not sure about the direct signals of the optispark and PCM? Do you test it plugged in? Also the PCM just acts dead. I can't pick up a signal with the scanner and my ses light does not come on anymore when I know it had trouble codes stored. Egr, 02...etc I know where the two shorted pink wires start on the switch I just wish I could know where they pin point too. I may need to search thru shobox scematics and try to locate where them wires flow.

timnfxr

The two pink wires on the ignition switch both connect to the same point on the switch (C2). One of the pink wires goes to the under-hood fuse block, and is the 12v input for fuses #9, #10, and #11 (injector/injector/ignition).

The other pink wire connects to the input side of i/p fuses #1, #5, and #10, (air bag/pcm ign/gauges).
Ignition Switch

NOTE: The above info pertains to a 95. You didn't mention what year you have.

You can use your meter to measure 12v (key on) at the fuses stated above to confirm the wiring.

4th Gen 4 Life

Ok Im getting 12volts to the PCM ign dash fusebox #5. Also I don't hear the fuel pump. Now the problem could be from my dash fuse box to the PCM. Or from what I see on shoeboxs schematic it also has a theft deterrent module it has to go thru? It has in the past not even turned over and showed a security light but my key resistor wires check good and the engine will turn over? I wanted to tune out the vats eventually but now can't even get the PCM to power on. That's another story tho. Thanks for the info so far fellas.

Chimera96

so have you confirmed you have FP with a gauge???

GaryDoug

The question about the pump was to ask if the pump was running not if the pressure was up. He can't start the car because of electrical problems. The pcm switches on the pump at startup. If that doesn't happen, the pcm isn't doing it's job. Seeing if the SES lamp cycles on and off would be useful also, which he did.

Chimera96

I was not aware the pcm sends signal to relay/fuse to activate FP, assumed it was key on activated direct to that circuit.

thank you for clarifying that point

4th Gen 4 Life

The fuel pump receives a direct signal from the PCM. My PCM is not getting power and all my ignition fuses are getting power. I really need to know what my main power wire is going to my PCM. I've seen the diagram of the PCM plus before but can't find it now? Plus I can't even connect to the PCM to scan it for code.

94 Z28 A4- ported heads/intake long tube headers. Egr/smog delete.

timnfxr

The main source of 12v power to the PCM is from the u/h fuse #8 (PCM).

Injuneer

That's the "PCM BAT" fuse. In a 94 it's in the panel at the end of the dash. Then there's ignition switched power to both the PCM and the fuel pump, fuse is also in the dash panel.

This is why EXACT year of the vehicle is important.

4th Gen 4 Life

So what about the PCM plugs does anyone have a diagram of that? If I know its getting power there and a signal from the ignition I could rule out my wiring and possibly change out the PCM. Or visa versa. It would make it a lot easier to track down the problem

94 Z28 A4- ported heads/intake long tube headers. Egr/smog delete.

Injuneer

Shoebox has the 95 PCM wiring diagrams on his website. Look at sheet 3 of 7. The wire colors and PCM connector/terminal designations are correct. The just moved the PCM BAT fuse between 94 and 95. In 94 it is fuse #4 in the dash panel.

4th Gen 4 Life

So do you think the 95 pcm plug diagram will have the same basics like the ground BAT and Ignition pinouts as a 94?

Also on this image i see the fuel pump is turned on by the IGN. so if im getting power to my IGN/PCM dash fuse it's possible to be shorted somewhere in that short distance because my fuel pump is not activating. Also Not sure if my TDM could play a role in this. Big thanks to shoebox to make all this a little easier to understand with his schematics.


94 Z28 A4- ported heads/intake long tube headers. Egr/smog delete.