O2 sensor replaced, code came back.

[essveeexxee]

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[SoCal LS-L]

Is your new sensor OEM or aftermarket?

[essveeexxee]

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[NiftySVX]

Your failed OEM sensor was better than the new bosch one. You need to remove it and replace it with a genuine part and I bet the code will go away. Bosch's retail line is a joke. That's why it's half the price of the new ones. I see this on toyotas all the time. The brand new aftermarket sensor won't perform within the range of acceptability of the computer. Somone replaced it before, obviously, because I can assure you subaru did not use bosch. That's why you had a repeat failure.

[redlightningsvx]

I got some Denso o2 sensors off ebay and they work great. They were $120 for both shipped.

[NiftySVX]

Denso is more likely to be compatable. They may have even been the OEM supplier, but I doubt it because Denso is a subsidiary of toyota and at that time Subaru was enjoying a close relationship with nissan

[essveeexxee]

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[essveeexxee]

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[Blacky]

Bosch is OEM on many, many Subarus including Outback, they use their spark plugs and wires too. I replaced both mine a year ago with Beck Arnley off Ebay and they have performed perfectly.

[redlightningsvx]

I used one of those Beck arnley ones and it lasted 2 weeks so I bought the denso.

[essveeexxee]

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[NiftySVX]

Okay so I don't have my 96 supplement but I am going to fudge my way through it. Since it's an OBD 2 car it's gonna be the same for a P0133 on anything.

That particular code is a slow response code, which means the control unit doesn't like what it is getting from the sensor on two consecutive trips. This means the fault occurs two times in two consecutive drive cycles, like in the morning to work it detects the code, (which is stored in memory as "pending") and then sees it again after the car is taken through another drive cycle, like on your way home, at which time the code becomes a "hard" or "active" code, and the Malfunction Indicator Light illuminates.

Before replacing an oxygen or air/fuel ratio sensor you obviously want to make sure the exhaust system is not leaking, as this could cause an erroneous reading from the sensor, though that wouldn't cause this code to illuminate, because the sensor would still report the information it received, that information would just be incorrect.

Quite honestly, I don't see anything else that would trigger this code. I suppose there could be a problem in the ECU. That is stretch though, in my experience. Any problem with the wiring would cause a different code to be output for an open or short. However, you may check the resistance between the sensor connector and the ECU, just on the off chance that there is some kind of high resistance in the harness or a junction connector. Again, I don't see how that would cause this code, but you could check it easy enough.

[NiftySVX]

Oh and to answer the rest of your question, the circuit it is checking is made up of the computer and the wiring to the sensor. Fortunately, this is an easy one usually because the circuit is so simple. There is also going to be some kind of high power circuit for the heater but that is not related to the P0133, there is another set of codes for open/short in the heater.

[essveeexxee]

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[essveeexxee]

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