ECU fried and 25 amp ecu fuse popped.

[SleeperTT]

So I'm driving down the road to get some breakfast after PT this morning and the car suddenly dies. 0 rpm's and I'm coasting down the road. I smell the faint odor of electrical malfunction in the air. I get it over to the side and pop the hood and the brown 25 amp ECU fuse is blown. I'm like ok. Replace the fuse and still nothing. So there I am no fuel and no spark and no ECU.

A buddy comes and we pull the car back to the unit and I pull the ECU and open it up and behold I have a fried pathway on the board. I've repaired a quite a few stereo amps with the same issue so I give it my best shot. I got the path way back together and make sure I haven't made a connection somewhere I shouldn't have and put the ECU back in the car and give it quick crank. POP goes the fuse again and my repair on the ecu has melted again. So here I am needing a ecu and a few 25 amp fusible links. :facepalm:

Now I've been searching since I got home and I can see this has happened before but everything I've read doesn't have a solution. I've seen some advice stating bad grounds or shorts in the harness but for this to all the sudden just happen is a little odd. I'm going to check all the grounds listed in the FSM.

Any other advice from the S chassis guru's. I'm a Z32 guru and this S13 is a hair different.

I don't want to put a different ECU in just to have this happen again. I have searched so no need to flame. If you know of a post that has some solid info about all this just post a link and I'll read it from cover to cover.

My car is a 93 auto s13 coupe

[SleeperTT]

So I take it there's no one on here that's ever heard of this happening.

[kruked]

On the ECU, is the trace burning at the back of the blue plug entrance? Take a couple of pictures where the trace is burning, please.

[SleeperTT]

It was. It was from the blue plug to the diode. There was nothing else in the pathway to the diode so I jumped from the wire in the plug to the post of the diode. Car starts up fine now but the odd part is it won't shut off with the key now. I have to pull the IGN link and the ECU link to shut the car off. The key won't come out of the cylinder until I pull the fuses. It will work for now while I wait on my replacement ECU.

I found a post about with the same exact symptoms and the poster said he heard a buzzing noise around the plenum. He also said he wiggled some wires in the area and checked his plugs. I did the same and with my repaired ECU its half way working. From what I seen in the area it looks like the IACV is in there. I know the IACV is on the same harness so I may need to pull the plenum and IACV and do a rebuild. If its like the one on Z32's it should be rebuildable. My idle flucuatates pretty bad at the moment. From about 500 rpm's to 1000.

Any ways here's my fix.

[SleeperTT]

Fixing the broken connection in the ECU tells me I have a intermittent short somewhere in one of the ECCS components. Unfortunately its going to be a ghost till it goes and stays gone.

[OnTheChip]

That pin is for the ignition switch, which tells the ECU when to boot up when ON, and when to shutdown the engine when OFF. You have a short somewhere such that that pin (p36) is being powered all the time so the ECU doesn't see the ignition switch open and therefore keeps the engine running.

[SleeperTT]

I was out messing around with the car today and found my short. It turned out to be the dissy harness. It had rubbed through on a sharp edge on the front right corner of the head. I took some pictures after I repaired the wire.http://i217.photobucket.com/albums/cc22/SleeperTT/The%20S13/IMG_1061.jpg http://i217.photobucket.com/albums/cc22/SleeperTT/The%20S13/IMG_1060.jpg

[OnTheChip]

Glad you found it!

[SleeperTT]

Well I'm not 100% certain. That is an issue I found and the car is acting right but only time will tell on this old car if that was the real issue or not. I may have just moved a wire somewhere while repairing that short. I'll eventually have a different setup but till then I have to make due with this one.

[SleeperTT]

Yeah now I'm 100% sure I didn't find it. I'm back to the car not wanting to turn off with the key. I pulled into the drive way today and went to shut the car down. Everything shut down except the Engine. Radio dies, dash lights die, engine keeps going. I popped the hood and started moving the harness around in the area that is shown in my picture's the car dies. Remember the key is in the off position. I look at the ecu and the red light is back on with the key in the off position. Next step is inspect each wire from the fire wall forward. Its getting annoying.

[OnTheChip]

Start pulling fuses one at a time until the ECU red light goes out. Hopefully that will tell you where the power is coming from.

Dave

[frankies1390]

ok im going to apply this cuz ive had it happen on a few other vehicles.. is ur 75 amp alternator fuse good? ive had 2 alternators go bad on me and it literally keeps the car running. have you swapped a different alternator or fixed someones existing wires to the alternator. if they are touching or rubbed through it will act as u are explaining i would poke around lower harness and alternator related parts

[SleeperTT]

I haven't looked at the alt area yet but will. The 75amp fuse is good and its acting like it should. The alternator is about two years old from what the kid I got the car from said. I know it was replaced because a friend of mine did the work. I'll look it over. Thanks.

ok im going to apply this cuz ive had it happen on a few other vehicles.. is ur 75 amp alternator fuse good? ive had 2 alternators go bad on me and it literally keeps the car running. have you swapped a different alternator or fixed someones existing wires to the alternator. if they are touching or rubbed through it will act as u are explaining i would poke around lower harness and alternator related parts