91 Legacy

 

I got a cel code for o2 sensor and put a new one in. Now it runs like crap. Black smoke out of the exhuast, sputtering, fuel smell, and dying. When I unplug the sensor from the ecu it runs just fine as it was. I tried clearing the code by disconnecting the batter overnight, but when I tested it this moring w/o starting the code was still present. Is this just a matter of resetting the ecu? Why won't the thing reset after 8 hours with the battery being disconnected?

 

I did use a after market OEM sensor, that I had to wire myself.

OLD NEW

red - white

white - white

black - black

Pretty sure this is the right connection.

If you used an after market 02 sensor, the kind that is generic, where by you solder your old connector to the wiring of the new sensor, then that could be your problem.

 

I have tried that several times, but could never get the new sensor to last long, or was sure that it was working correctly in the first place. I think it has to do with the soldering. You just can't count on the soldering job to carry really sensitive electrical values to the ECU.

 

I am banking that replacing the 02 sensor with one specifically made for a Subie will fix your problem.

Front O2 sensor should always come from Subaru, and this is the reason why.

I've had good luck with the better quality aftermarket sensors, soldering and all. I doubt very much that the culprit is the soldering job (well, unless the wires were mixed up - you might try switching the red and white ones). There's really nothing sensitive or complicated about an O2 sensor. It simply generates a voltage relative to the O2 concentration, say 0.1 to 1.0 volts. A soldered connection would no more impede or otherwise alter this voltage than the plug would, it may even offer less resistance then the plug. Now, if the new sensor sends out a significantly different voltage than a Subaru spec sensor at a given O2 concentration, that could be a problem. This could result in the car thinking that the fuel mixture is too lean or too rich when it really isn't and making automatic adjustments accordingly, which, of course, would make the car run like crap. You could probably test the sensor with a volt meter once it's up to operating temp. Of course, you'd need the factory specs to compare it to - maybe that info is out there.

91 Legacy

 

 

OLD NEW

red - white

white - white

black - black

 

you wired the signal wire to the heater circuit.

 

 

old NEW

Red Black

White White

Black White

 

 

* edited......better chart bellow*

Edited August 15, 201015 yr by Gloyale

Front O2 sensor should always come from Subaru, and this is the reason why.

 

It's $150 at the dealership right?

Front O2 sensor should always come from Subaru, and this is the reason why.

 

One should never say always, nipper. Would you care to elaborate on why you feel this is the reason?

Ok....actually since FSM doesn't have wire colors on the sensor itself....let's try this again using the Body Harness side of the connector and match that.

 

So it would be like this:

 

Body <> New Sensor

 

 

White <> Black (signal wire)

 

Yellow w/red <> white (heater power)

 

Black w/white <> white (heater ground)

Yeah, I was thinking I must of wired it wrong. So the White Wire on the old is the signal wire not the black. That makes sense. I'll change it tomorrow and see how she goes. Thanks all

 

Yep I mis wired it. It's fine now.

Edited August 16, 201015 yr by hustle

If you got the cash to spare, I'd say go with the OEM. I didn't and went with the u-wire-it sensor from Advance. Looks to me like the factory sensor in my car was made by Bosch...and looked just like the parts store Bosch no-plug sensor.

 

Course, my car ended up throwing the same headache code a few hundred miles later, but I don't think the O2 sensor needed replaced in the first place. Runs the same as before. MPG is actually 1 better than previously calculated.

 

 

Glad you got the wires figured out. I was paranoid about that too...lol.