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2G absolutely no electrical power

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Nasty Dream

10+ Year Contributor
455
3
Aug 30, 2011
Alexandria, Virginia
I have to apologize because my question cannot possibly have a positive answer. But I really just need to know if the computer in a 1995 GST is required to be operational for the car to have any electrical power.

I parked my car in my mom's parking lot for about 8 months with the battery removed and on a maintenance charger. It was running fine. I only parked it because I have 2 jobs working from home and didn't want to keep it insured since I have access to 4 other cars.

So the story goes: I removed the battery and pulled the computer to investigate it. But in that time, I did nothing with the computer after all. 8 months later, I just plugged it back in and installed the battery.

But there's no lights, no sign of any power. I used a battery tester the battery is perfect.

If there computer is shot, shouldn't the headlights at least work? I found a mouse nest in the curve of the intake manifold and I removed it. I see no sign there's something wrong with any of the wiring or fuses.

BUT I know mice had eaten the wires of my stepfather's truck and he needed a new harness. Do you think I might need a main wire harness too? The little bastards.
 
I don't know where to start. I have about a couple of hours to work on the car before I have to give up and sell it.

OK this electrical diagram will be really helpful.

http://dsm-club.org/doc/pdf/2g/electrical/96_ELECTRICAL_WIRING.pdf

I wonder if mice ate the ignition switch wires (where you put the key in) :p

or just a fuse or something. I checked the main fuses and they seemed fine. You can see them through the little windows. And I've never had any problem with any of the fuses.
 
It would be hard to say that a wire is chewed if you haven't looked through it all. I imagine a mouse cold have chewed through one, but you will never know until everything is inspected. If the ecu is shot, you probably won't get much electrical from it. It is the car's brain after all. I highly doubt just letting the ecu sit unused for 8 months would hurt it in any sort of way without interference from something else. Pull the case off the ecu though so you can inspect it for leaks or damage. If you end up needing another, I do have a spare '96 gsx (with manual trans) ecu.
 
The car should still have power with a bad ecu. Try running jumper cables both the red and black to the negative terminal on the battery. Nothing to the + positive. And one to a good ground on the body such as a strut mount bolt. And the other to a good ground on the motor such as the power steering pump bracket.
 
Thanks for the suggestions.

Now I recall being able to leave the headlights on without even having the key in the car. So at least that eliminates the ignition switch as a culprit.

It's well grounded. I recently had gone over it and installed the thickest wire I could find for ground to the intake manifold and to the body of the car and I think there's another one going somewhere - the transmission? (can't recall). I used copper cables and filed-down and cleaned the mounting locations.

I'm not sure exactly how the wires route because the positive goes behind the engine where I can't see. So I don't know where the wire goes to first from the battery. So I don't know where to start looking for breaks in the wire...

I would love to be able to swap a different ECU in the car at least just to test it. I have a 1995 GST manual, won't the GSX one be incompatible?
 
It's still a turbo computer and the correct year. It doesn't care if the car uses 2 more wheels to drive with.
Grab your jumper cables and ground them on the battery and go inside the cabin and clamp the ground to a stud or bolt or anything metal just as a test that you have good ground to the cab area. You might be surprised, but at least it will rule out a bad ground.
 
From the (+) battery terminal, there's only 3 cables originally. There is the large gauge cable going to the starter and two dual-wire cables going to the fuse box. They go to the indicated sides of the 60A Fuse(+B) Fusible Link and the 100A Alternator Choke Fusible Link. From there -- and through the fuses -- everything else in the car receives positive voltage.

These can be checked with simple continuity tests between those wires at the fuse box and the (+) battery cable at, but disconnected, from the battery. Alternatively, leave the (+) hooked up to the battery and between the indicated sides of those fuse holders and a ground, there should be battery voltage measured with a voltmeter.

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I had one more idea -

The ECU case on mine is metal. I know from experience with computers that being grounded might be necessary for it to work, but I didn't think of it at the time. I did not fasten the ECU to the car. I just plugged it in hanging there.

Well, it's worth a shot but if anyone knows one way or another that would be very helpful.

(Example image)
http://tech.mirage-performance.com/ECU/EPROM-ECU.jpg
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The ECU being bolted up doesn't matter.

What have you verified up to this point? You've received a number of suggestions, what is still missing?
 
Since you mentioned the larger gauge cables from the starter and the other dual core cable, it made me think of something from long ago. On your positive battery cable, what all is hooked up to it? Can you post a picture of that?
 
"The ECU being bolted up doesn't matter.

What have you verified up to this point? You've received a number of suggestions, what is still missing?"


Yes, thank you for your suggestions. I figured it didn't need to be bolted up but wanted to know to eliminate the possibility.

I have not visited the car since. I no longer need to move it immediately but still need to get it working eventually. I want to be prepared with some ideas when I get there to work on it.

I will bring my phone and laptop with me and upload some pictures if I need anymore help from the scene.
 
Turns out that - while there were several wires hooked up to positive terminal - the two white wires that go to the main fuse box were not connected. D'oh

They were kind of hidden, tucked underneath the upper IC pipe. I only noticed when I was standing next to the battery location on the side of the car.

Glad I didn't worry too much. I figured it was something like that.

Your suggestions were invaluable and I thank you all for helping me troubleshoot.
 
Glad to hear you got it figured out. That's exactly what I was thinking when I mentioned it. Those white wires go to your alternator. They came loose on one of my old DSMs and it took me a bit to realize what they went to.
 
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