I'm getting MIL code for the O2 sensor gone bad, etc. How can I determine which of the two sensor is the bad one? There's one near the engine (manifold) and another on the cat. converter.
thanks,
Mel
96 Cherokee
Generally it's the upstream one. If your getting a "catalytic failure" or similar it could be the downstream but in most cases its the upstream.
Actual diagnosis requires test gear.
Just remember to never get any RTV type sealant anywhere close to the sensor. The gasses that stuff gives off will kill them.
This is why MIL codes are pretty much useless. You need the OBDII trouble code. It'll be very specific regarding which sensor and what the actual fault was.
On that thought, PepBoys (and probably some others) will read the codes for free. Actually the lower end OBDII readers are fairly inexpensive.
Well, some are.. I know PepBoys used to carry one for about $30 that only could read.
AutoZone does this too. At mine (before I got the OBDII tool) they would come out and do it for me [because they knew how to do it fast and I would not walk off with it]. If I wanted to clear the codes they would let me push that button.
Always get the codes first. Then bring them here for advice. Then decide what to do. Tomes
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