Over the weekend me and two friends bolted up several things to a 2004 wrx

up pipe (with the 2.2k 1/2watt resistor)
down pipe
mid pipe
race pipe
Oil Pressure
EGT
CEL fix here

After everything was bolted up an experienced electrician wired the car for the 2 new gauges and the CEL was wired into the O2 line.

Heres the chain of events...(car was cold for 24 hours)
1) We turn the key to accesory and the fans turned on.
2) Turned the car over and it started
3) Got CEL
4) We let the car idled for a few minutes then the gas gauge dropped to empty (from half full) and the light came on...
5) Turned car off and started to inspect things

First thing, the CEL fix that was wired into the O2 line was FRIED..the lines were destroyed



We then wired it up without the CEL fix.
Car started still had CEL (pulling O2 sensor codes now) We turned the car off again
Gauges still wacky

Removed all new wiring (try to revert back to stock wiring) Im thiking its a grounding problem here.

Now car wont start at ALL..
The CEL was poorly lit like a dead battery and the engine wouldnt start( would crank but nothing more) Our ODBII scanner kept reading no link so we went after the ECU.....
After we got the flooring up we noticed how hot it was (real hot)

We unplugged the battery

We Then examined it...took it apart and noticed the following
One slightly burnt pin (nothing bad) and a diode (number D509) with the letters D.4 and a number 2 on it...it was charred and busted....any other diode like this on the ecu had anywheres from 23.6k ohms to 40.1k ohms this was pulling about 6k ohms...

what to do??????
Im thinking of just trying to find another diode like the others on the board and replacing that diode...everything else looks fine.


over in the 2.0l turbo forum, I have a thread there too:
http://forums.nasioc.com/forums/showthread.php?s=&threadid=521610


ANY HELP would be so tremendously appreciated

The CEL fix might have accidentally been wired into the heater circuit for the 02 instead of the signal line, causing the heater driver circuit to burn out. Just a guess from what you've posted.
I don't think you're going to be able to fix it just by replacing a diode. First you don't really know what type of diode it is, may be a specialty part and not something you can get at Radio Shack. Also it is very likely that other components are damaged as well, and possibly the circuit board itself. I haven't examined the PC board in a Subaru ECU but it may be a multi-layer board.
The fact that your scanner reads no link reinforces my feeling that the ECU is done. I'd look for another one.
Also check the ECU fuse to be sure it isn't blown before trying again with a new one.
FYI, you can't accurately test diodes with an ohmeter, especially a digital one and when they are still in the circuit. Most digital meters have a diode test mode but depending on what is connected across the diode it may need to be removed from the circuit for testing.

Thanks for your reply.


We went through the entire car, looking for burnt wires and fuses, we couldnt find anything other than the mess that became of the o2 harness, we spliced in fresh wire in place of the burnt pieces

There was 1 wire going into the ECU that looked like it got very hot and we replaced that as well.

No blown fuses anywhere, the door locks, lights, horn, etc all work fine, the gas gauge reads correctly and the fan no longer kicks on for no reason.

I have a new ECU coming today and after triple checking fuses again tonight, I'm going to install it.

Thanks again for replying.


PS: Where is the ECU fuse? I want to make sure I have checked it.

Mulder:
Does the ecu ever get warm..like should it be warm to the touch ever? Im trying to determine if its normal or if a wire is shorting out???

thanks so much man...

Never felt one in operation, I'd think it may get somewhat warm but not blazing hot.
I'd have to check to be sure which fuse it is, IIRC it may be labeled "IGN".
Just triple-check before installing the new ECU that the fix is installed properly, you wouldn't want to cook another one. Be sure there is no connection between the heater circuit and signal wire, that would be very bad.

Originally posted by Mulder
Never felt one in operation, I'd think it may get somewhat warm but not blazing hot.
I'd have to check to be sure which fuse it is, IIRC it may be labeled "IGN".



If you could check and let me know before 5pm today you would be my hero lol

also maybe if you could tell me if it gets warm under normal conditions, ANYTHING you could tell me would be tremendous help

I'm at work until well after 5, won't have access to my manuals until I get home later. No way to check for ECU operating temp, you could try posting the question in the Engine Management forum.
Look in your owners manual for fuse info, it may be in there.

thanks a bunch, i will