Ecu not receiving power signal... possiable fried #62 ecu?

[teamsprock]

I have spent the last few days searching online and working with a multimeter in the car trying to diagnose my issue, so if I missed something searching, please help direct me there and sorry for starting a new thread.

Quick background: had car running fine last year, spent the last few months working on car, new intake manifold, painted interior, and relocated lower engine harness (the one with the two black fuse boxes in the enigne bay) into the cabin. Now car won't start.

Car Specs: 89 240sx, redtop SR, #62 mines flashed ecu

Good: Fuel pump primes, all lights work, car turns over, 12v power to coilpacks.

Bad: No power going to ecu (see explanation below), when the key is turned on the ecu led blinks once then stays off, no spark signal sent (assume because ecu has no power), haven't check yet to see if injectors are firing.



Since my ecu light doesn't stay on does that mean it's done for? I read that on another forum, but to much bad info in the thread to be 100% sure.

If I check for voltage on pin 38 or 47 ("ecu power") on the ecu clip I get nothing. I assume that being the "ecu power" I should get a 12v signal?

More info: I used the clip circled in red to send a 12v signal one at a time between those 3 power sources to identify which one did what if anything. When I give power to the main ignition power the ecu led flashes once and AFC turns on. If I give power to the backup power, nothing happens (what I would expect). If I give power to the ecu power, the AFC kicks on but I don't get any thing happening with the led light.

Thanks for the help.

[koukimonster139]

Originally Posted by teamsprock

relocated lower engine harness (the one with the two black fuse boxes in the enigne bay) into the cabin. Now car won't start.

I would think without looking at it that this is where you should start.


Also, did it get power before the re-flash or did it run using the mines tune before?

Sounds like a wiring mix up

Im also confused where you said "when you turn the key on, the led flashes once", does this mean it is getting power?

[teamsprock]

Originally Posted by koukimonster139

I would think without looking at it that this is where you should start.


Also, did it get power before the re-flash or did it run using the mines tune before?

Sounds like a wiring mix up

Im also confused where you said "when you turn the key on, the led flashes once", does this mean it is getting power?

Ya it ran fine with this exact setup, minus the new intake manifold all last year. So yes the wiring that I changed is exactly where I started and what concerns me the most.

In the bottom of my post I noted that the ecu was getting power via "main ignition power". (The comments on red in the picture are the voltages I measured)

I found this info today so I will start seeing what power sources I might be missing and then figure out from there why they are not there. Probably be this weekend before I get a chance to work on it again.

#62 Ecu pinout:
These pins should have 12v when iginition is on: 4, 25, 38, 46, 47, 109

Pin 34 should have voltage when key is in start position

Grounded Ecu pin's: 6, 13, 39, 48, 107, 108, 116



****UPDATE:
I solved the problem last night and got the car running. Two problems were found. I had a bad ground wire and that is why I was not getting power to pins 38 and 47. But the bigger problem that was keeping my car from running and making me think that my ecu was dead was the screw that switches it between diagnostic mode and regular was right on the line between the two. So once I turned the screw counter clockwise the ecu LED stayed on and things have been running great since then. So yes a working ecu will have the LED light on when the ignition switch is on and then the light shuts off when the car is running.