Upstream O2 Sensor

[lr60]

I've had my 03 yellow Baja for about 4 years (165000). When I first bought it, it had a constant "check engine" light showing a P0031 (upstream oxygen sensor.) I replaced the O2 sensor and it starting throwing P0031 and P0030 codes. I GAVE UP and drove it for years like that.

After an alternator problem, I got an itch to try to fix this thing again. The codes that were being thrown were P0030 (multiple) until it sets off the check engine light. I tested the old sensor and the heating element was HOT! I broke down and bought another sensor and installed it. Well, it too, throws the same codes.

Does anyone have any suggestions? What is the ECU looking for on that line?

[Hawk296]

Have you checked the wiring down to the sensor as well as the connector? Were the 02 sensors you used a Subaru part or a generic one from an auto parts store?

I am not sure about the Non turbo Baja, but does it have a relay on for the 02 sensor heater behind the dash by the main relay like the outbacks do?

[lr60]

It is an auto parts sensor, not factory. I have to wait to check the wiring, my alternator failed again and I have to get that fixed.

[lr60]

UPDATE: I finally got the Baja to stop throwing the P0030 codes. The problem turned out to be the new autoparts store oxygen sensors. While the cross reference did state they would replace the Baja UPSTREAM sensor, it was off enough to throw the codes. Another weird aspect of this is the bad oxygen sensor was marked as a Denso part with number. However, Denso had no record of that part number...no real surprise there.

The bottom line is that if it is NOT the original Subaru sensor (big bucks) then it must be a Bosch 15501 Wideband A/F (air/fuel) Sensor. And if the price is under a $100.00 then it is the wrong sensor...