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Question on O2 sensors...

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My brother pulled the codes on my '97 wagon and we got a knock sensor code (ok I'll replace that no problem) and an O2 sensor code (P0135). My question is, how many o2 sensors are there on a 2.2L ? and how do I know which one to replace? :confused: I think this may be the source of my rich condition. I'm going to be doing a major tune up when Uncle Sam pays me back and I want to know how many/which o2's I need to get... Thanks in advance, fellas!
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depending on the miles and age of the o2 sensor,

it could be that the sensor heater is bad.

or it could be a simple wiring problem, or a short.


so look at the wiring before you buy.

look for cracks, bare wire, mouse damage, broken connector.


if you do buy,

do NOT buy a cheap generic o2 sensor.

the front sensor needs to be subaru quality or BETTER.

a cheap unit can cause headaches and trouble codes from the start.



95 - 99 suabrus have 2 sensors, both on bank one.

bank one is the exhaust side attached to the #1 cylinder side of the engine.

since both o2 sensors are after the 2 sides of the exhaust combine, after the y-pipe,

there is only one bank.

front sensor is in front of or in the cat,

rear sensor is after or behind the cat.

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i do not remember the pxxxx code,

but a few years ago a o2 sensor code came up in the winter.

i searched a couple of forums for the code and the cause.

i a surprisingly found that the code was posted most often in winter,.


i concluded that it was a rain, snow, slush, salt, sand induced code.

in other words, crap on the road in the winter got into the connector.

i do not know if this is accurate,

and i do not know if it was the p0135 code,

but i would put some dielectric grease in the connector when you check or replace it.


it can't hurt.

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Generally yes. They sometimes rust in the threads and you will probably have to remove the heat shield to gain good access.. Buy some short nut and bolt sets as the shield bolts will either break or round off requiring cutting. A cut off wheel of any type will make it easy here.

I generally hold the bung with an open end and turn the sensor with another. (because I've had one completely wrench out the weld and didn't want to have this happen again). Warm the engine a little and PB beforehand.



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