Failing ECU? - Subaru WRX Forum
 
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#1 Old 06-19-2014, 03:22 PM
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Failing ECU?

2003 WRX. I'm still having problems with my car just losing electrical power while driving. Replaced the alternator....twice. Cleaned the grounding points on fenders and firewall. Charging at 14v. Problem goes away, once I shut the car off, then start it again. Could this be a sign of a bad ECU? The whole car shuts down when this happens. Rpms drop and everything. Car bucks like hell.
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#2 Old 06-20-2014, 01:46 PM
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Plot twist. Noticed the area around the ignition was warm. Pulled the dash fuse panel out, found this blue wire that's coming from parts unknown, amd running to my ignition. (Maybe the other end is going to the AF gauge, that's not even useable but has power) I have a feeling this may be a good lead into what is going on. How tricky are ignition switches? I've never messed with one.
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#3 Old 06-20-2014, 02:19 PM
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Plot twist. Noticed the area around the ignition was warm. Pulled the dash fuse panel out, found this blue wire that's coming from parts unknown, amd running to my ignition. (Maybe the other end is going to the AF gauge, that's not even useable but has power) I have a feeling this may be a good lead into what is going on. How tricky are ignition switches? I've never messed with one.
If your having issues with your ECU it would be unlikely to start in the first place. that and it wouldnt kill your headlights if your ECU failed while driving, that sounds more like a bad ground or faulty battery/alternator. I know you replaced those so lets start looking for vampires sucking all the power. It could be a single wire with worn sheathing arking with ground. as for the Blue wire, 22-28 gauge Blue is usually reserved for Aftermarket stereos its known as a "remote" line. Its a very low amperage 12V line used to signal to components that the vehicle is on. thats why most installers choose to tap into the ignition fuse box with a piggyback. Its also not un-usualy for your ignition to get warm during use. Unless its about 85 degrees farenheight then i wouldnt worry too much about ignition warmth.

Unless there is an aftermarket stereo or amplifier with something very wrong then I dont think the blue wire would cause the kinds of issues your having. ( that assuming someone is following normal wiring convention and didnt just use a blue wire because it was what they had lying around)

From your description it could be a number of things but a ghost in the electrical system is not usually easy to find. If your comfortable with electrical I would start by replacing your grounding straps. That way your ground is nicely isolated. then I would pull non-essential fuses 1 at a time with it running to help you isolate the culprit.

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#4 Old 06-20-2014, 02:27 PM
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The battery has not been replaced. My understanding is that even if the battery was not hooked up while running, this shouldn't make any difference in driveability. Even one with a dead cell hooked up. What grounds directly correspond with these failures? I could rule out grounds that just go to "non essential" components of my car, at least.
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#5 Old 06-20-2014, 02:33 PM
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The battery has not been replaced. My understanding is that even if the battery was not hooked up while running, this shouldn't make any difference in driveability. Even one with a dead cell hooked up. What grounds directly correspond with these failures? I could rule out grounds that just go to "non essential" components of my car, at least.
I did stereos for a while and we used to swap all the engine bay grounding straps for aftermarket grounding kits, or DIY ( Home depot wires, eyelets and grommets ) usually 2 on the engine, 1 on the firewall and 2 on the chasis. I would also check the grounding wires under the dash, Just to make sure everything is grounded first.

Then I would pull fuses rather than disconnecting grounds. to make sure something like your wiper or AC relay isnt causing the issues.

Do you have an aftermarket stereo or amp? thats the first thing i would disconnect if you have one.

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#6 Old 06-20-2014, 02:34 PM
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Oh, and factory radio as well.
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#7 Old 06-20-2014, 02:56 PM
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Where are the grounding wires under the dash?
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#8 Old 06-20-2014, 04:05 PM
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Typically there are 2 attached to the firewall left of the drivers footwell and a few behind the factory stereo. Usually you can trace the black lines out of the factory wiring harness to lock rings gromets. I would focus more on the grounds in the engine bay, its more likely they would cause the kinds of issues your having.

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#9 Old 06-21-2014, 05:06 PM
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This is what I'm talking about. Blue taped to purple comes from up further into dash, out to firewall/engine. Other blue wire connected somewhere on the cruise/fog light panel.
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#10 Old 06-24-2014, 06:06 AM
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Well, for anyone keeping tabs or striken with curiosity, that looks like the power wire to the afr gauge. It's routed into the cruise panel. Everytime I have a loss of power, the system is overcharging and cutting out. At the mechanic (yikes, first time in a while) to get fixed up.
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#11 Old 06-28-2014, 04:17 PM
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#12 Old 06-29-2014, 03:26 PM
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Wire ended up being irrelevant to the issue, as noted by scythe. (What a know it all, that guy) haha. It was a felt terminal protector somehow disturbing the connection to the battery and overcharging the system. Haven't had a hiccup since removing it.
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#13 Old 06-30-2014, 11:29 AM
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Wire ended up being irrelevant to the issue, as noted by scythe. (What a know it all, that guy) haha. It was a felt terminal protector somehow disturbing the connection to the battery and overcharging the system. Haven't had a hiccup since removing it.
Now thats one Ive never heard of, not a loose terminal just a corrosion pad freaking out the system. Ill add that to my troubleshooting list from now on.

Those pads have never seemed to work for me anyways, they usually just get all furry and white. I usually recommend swapping the standard terminals for something enclosed like a quality distribution block or using some battery terminal protector spray. It keeps 02 out of the equation and keeps the anode from oxidizing.

Thanks for getting back to us, Glad to hear your back on the road again

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#14 Old 06-30-2014, 12:08 PM
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Yeah, I've heard of this happening to hondas from some other guys. I doubted that was going to fix it, but it's holding strong, man.
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