ECU Power Short (Thinking out loud)

[KillerCam282]

Situation:
Battery has full power. Ecu power is clicking on and off randomly and recieves partial power. ECU led remains off when recieving partial power and engine lights are dim. The starter won't crank via ignition switch.

What Happenned:
A fuse should have blown but didn't. I saw smoke, most likely from a couple burnt wires.

The Cause:
I tried to start the car up off the charger set on 50 amps. ( I knew I should just let it charge the battery)

My Exploration:
When I powered up the car from under the hood (hooked up a power source directly to the fuse box) the ECU got power... Fuel pump kicked on and everything. Starter turns from under the hood. Car will run when powered up directly from under the hood.

To Be Deduced: ECU power source is shorted somewhere between the cabin and the hood. Since the starter and ECU power source went at the same time, its highly likely the short is at the same location. I have not went indepth with the schematics to find a connection between the starter and ECU power source. I am ruling out a break near ECU fuses. The ECU and starter must share some sort of switched ignition power. This has to be where the break is.

Its raining hard. If it weren't, I would be outside finding this damn short.

Any input is appreciated. Just no mis-info, like main relay, ignition switch, etc... Those are not related at all to the problem. Its a bit more complicated than just replacing a part.

[SteveB]

Situation:

What Happenned:
A fuse should have blown but didn't. I saw smoke, most likely from a couple burnt wires.

Well, which fuse should have blown?
Where did the smoke come from?

[KillerCam282]

Smoke was on the driver side. It was not strong so it may be deep under the dash. I will look up the schematics when I get home.

[xfactortype1]

you very well could have fried part of yur ecu doing that. other things you might consider, or considered as possibly fried are your eld system, starter itself or solenoids, and maybe alternator. hope it helps and good luck

regards tomd

[KillerCam282]

you very well could have fried part of yur ecu doing that. other things you might consider, or considered as possibly fried are your eld system, starter itself or solenoids, and maybe alternator. hope it helps and good luck

regards tomd

My Exploration:
When I powered up the car from under the hood (hooked up a power source directly to the fuse box) the ECU got power... Fuel pump kicked on and everything. Starter turns from under the hood. Car will run when powered up directly from under the hood.

You might have missed this. It runs fine when powered under the hood. The ignition signal is not reaching is the problem.

[xfactortype1]

Situation:
Battery has full power. Ecu power is clicking on and off randomly and recieves partial power. ECU led remains off when recieving partial power and engine lights are dim. The starter won't crank via ignition switch.

What Happenned:
A fuse should have blown but didn't. I saw smoke, most likely from a couple burnt wires.

The Cause:
I tried to start the car up off the charger set on 50 amps. ( I knew I should just let it charge the battery)


quoted from above..

i know some car have a fusible link in the ignition switch circuit..think its a white wire, but i also think it pertains to wagons though. im not sure

you probably did burn wire that youll have to trace down via the schematics and replace. now you say no fuses were blown, but what about a burnt fuse. do you think it would cause your problems. i think its fuse #2 under the dash that has the ecu on it. im sure theres others.

good luck though
regards tomd

[Dirty Harry]

I tried to start the car up off the charger set on 50 amps.

HAAAAAHAHAHAHAHA

anyway

shit dude. I'm suprised you even tried that, not to mention such a small charger. Anyway, are you all right dude? You already found your problem if everything is fine when fed from the fuse box but not from the battery terminals...just trace the shit out.


...wtf...I still don't believe this is the real AcclipseH23

[KillerCam282]

HAAAAAHAHAHAHAHA

anyway

shit dude. I'm suprised you even tried that, not to mention such a small charger. Anyway, are you all right dude? You already found your problem if everything is fine when fed from the fuse box but not from the battery terminals...just trace the shit out.


...wtf...I still don't believe this is the real AcclipseH23

ROFLMAO...I do things knowing its wrong...I was just taking shortcuts and well wound up with a short... .

Yeah, I couldn't wait to start it up. I got too excited since I finished everything up. The Optima was super dead. So I charged it for like 1 hour, and it only had enough power to turn the ECU on and run the fuel pump. Cranking was not in the picture. So I said fuck it, I have no time to wait and raised the charger up to 50 amps. Then I cranked, and cranked and...poof.

Tracing is a bitch only because it takes forever. I will find eventually. I mean, it cant be that hard to find!!!! The freaking wire turned itself into a fuse and blew. So yeah still looking for some black charred up wire.

[KillerCam282]

Even worse, I could explain thoroughly why that is a stupid thing to do. Most likely I'd also scold anyone who did that or thought of it. Yes, I am so hypocritical.

Ah, I slay me. Well more fun...when the weather can make up its mind, I will fix it. Most likely I will take care of this by Tuesday. I will update then.

I'd like to Cha-Ching myself on this one.

[StickyDilJoe]

You have a bad ground and your car, like most honda's, will look for the next closest thing to a ground to the chassis, which is your throttle cable. Nothing is shorted, yet. Lights are dim and shit is smoking cuz everything is grounded so there is power going to everything at once. Solution: Find where the bad ground is and replace the throttle cable, cuz most likely by now, it's melted and grounded to your firewall.

[cp[mike]]

Ah, I slay me. Well more fun...when the weather can make up its mind, I will fix it. Most likely I will take care of this by Tuesday. I will update then.

I'd like to Cha-Ching myself on this one.

eh, even after i had done my first own motor swap (which would mean i hope i at least kinda knew what i was doing with a car) i hooked up my battery backwards and the car completely lost all power... i posted up on accordtuner freaking out, asking what i could have possibly blown. i was called Battery Boy for a while after that...

so dont feel stupid, everybody has a story like this.

[KillerCam282]

eh, even after i had done my first own motor swap (which would mean i hope i at least kinda knew what i was doing with a car) i hooked up my battery backwards and the car completely lost all power... i posted up on accordtuner freaking out, asking what i could have possibly blown. i was called Battery Boy for a while after that...

so dont feel stupid, everybody has a story like this.

Thanks Joe, You know...I was leaning that way (looking to blame a ground)... on that. Mike thats hilarious... My friend wired his system backward and the same thing happenned. He was flipping out and going all crazy. When i checked his wiring I busted out laughing. I mean they color code the wires for a reason...

[Dirty Harry]

You have a bad ground and your car, like most honda's, will look for the next closest thing to a ground to the chassis, which is your throttle cable. Nothing is shorted, yet. Lights are dim and shit is smoking cuz everything is grounded so there is power going to everything at once. Solution: Find where the bad ground is and replace the throttle cable, cuz most likely by now, it's melted and grounded to your firewall.

It is true, according to basic laws of electricity, that if your main ground breaks the other ones will be more stressed of course, assuming the AWG of those wires isn't as large as the one that broke. Therefore you will have a few leads carrying a much greater ampere load than they can sustain reliably.

But, something you said makes absolutely NO FUCKING SENSE AT ALL. Let me requote:

Lights are dim and shit is smoking cuz everything is grounded so there is power going to everything at once.

WTF... you better explain this because it sounds exactly like somebody that doesn't understand electricity properly

[ACCLUDE91]

I was working on a Towncar a few years back and the battery died. I stuck a charger on it at 12 amps and just let it sit for a little while. It still wouldn't start so I turned it up to 75amp start and tried to start it. It did start, but the digital gauge cluster went nuts and eventually stopped working altogether. I had to replace the damn gauge cluster before the guy came to get the car. Plugged the new one in and it worked perfectly. A flaw in the wiring/fuse locations? I don't know, but it happened so there's a chance you may have fried the ECU.

[KillerCam282]

I was working on a Towncar a few years back and the battery died. I stuck a charger on it at 12 amps and just let it sit for a little while. It still wouldn't start so I turned it up to 75amp start and tried to start it. It did start, but the digital gauge cluster went nuts and eventually stopped working altogether. I had to replace the damn gauge cluster before the guy came to get the car. Plugged the new one in and it worked perfectly. A flaw in the wiring/fuse locations? I don't know, but it happened so there's a chance you may have fried the ECU.

I doubt it. Only because the car ran from under the hood. And I also tried like 3 ECU's in my collection. All had the same problem. The power supply to the ECU was shorted. Still tracing for breaks.