milto0n

Hey guys, picked up another project for the summer and could use some help. It is a 1993 with stock dual cam motor. Basically, the car has no ECM power, no red led light on any of the three computers that I've used. Obviously, this causes no fuel pump priming and no spark to ignition components.

All fuses and relays have been replaced with multiple others so that is not the issue. The car cranks very well but doesn't turn over. Battery and all ignition components are fine.

My question is what wires are directly involved with power to the computer, from the ignition switch to fuse boxes to the actual computer. On a similar question asked on the forums someone stated that the grey plug near the battery gives it power but I could use a little more detail. Any help would be greatly appreciated as I've got a long day of wire tracing. Thanks.

milto0n

Aright everyone I learned a lot about wires today... On a second car I unplugged things in the engine bay one at a time to see what was responsible for lighting the LED up on the ECM and I found the grey plug by the battery (8 pins I believe?) to be the one (as I mentioned before.) This leads to the ignition switch which again was working fine (tested on donor car.)
On the donor car, I unbolted the grounds on the drivers side block (right next to the o2 sensor wire) and found that doing so kept the light from turning on. I look over on the non op car and sure enough it non functional grounds at that point. Cleaned that good but still no light. Switched out ECUs and there it was.
However, as I figured, when I went to crank the car, it did not turn over and some smoke came from ECU. Upon undoing both the now fried ECUs I have, there are burns in the same location.
The ECU pin burned is 36 which is the 12V ignition switch. I'm going to search now but if anyone has any useful information, I'd appreciate it. I'll make sure to keep this updated just in case anyone has similar issues.

milto0n

Updating again everyone. I know it's difficult to offer suggestion since it's impossible to know what's wrong without the car in front of you but any info is still appreciated.

Anyways, as I mentioned before pin 36 which is the ignition switch (12v) keeps buring. here is the picture:


Anyways, tracing this black/ red stripe wire leads to nothing really. Continuity along the entire stretch of upper harness. The interesting thing though is that when I jump over the broken trace with the a small length of wire, the EGI/ EGI pump relays both click and the ecu light turns on (key to the on position). When the key is taken out, the light still stays on. If I go to crank, the light turns off and it begins to smoke from that trace again. The only way to turn the light off is to un plug the ecu.

The only other thing I can note is that the mafs was a hack job wiring (removed the shoddy wiring) and the EGI relay becomes warm after jumping pin 45 in the ECU.

milto0n

Fixed the problem. The problem was with faulty mafs wiring. I hooked up a wire to temporarily fix the burnt trace and sure enough the car stared.

Driftwire

Same problem i soldered a new wire in the ECU to fix the burn trace and my ECU comes on.

For any1 looking or having this issue its Pin 36. And its the 12v Ignition Switch

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zfan

I have a 1990 240 sx and the ECU isn't getting any power ( no led ). Obviously my coil isnt firing even though im getting fire to the ICM and the coil. ??? I really can't understand that. But anyway if somebody could please help me understand how to push power to my ECU I would be very grateful.q

kyral

Black red wire at the grey connector under the hood. its hot on ign and provides power to the ecu and the ignition coil.
you can jump a (fused) 12v wire to this B/R for testing

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