02 sensor problem

[nickorsi]

I have a 98 Mountaineer 5.0L I recently has my CEL light up and upon getting diagnosed at Autozone I found that the code relates back to the O2 sensor. I don't remember the code, but thought it was for bank1 sensor 1 ... which I had replaced last year before getting my inspection done.

I also was told by a local shop around that time that my CAT was glowing red.

Could my CAT be bad which in turn is setting off the code for my O2 sensor?

Thanks

 

[my98nnj]

Sensor 1 would be before the cat.
But, if the cat is glowing red, it's most likely shot and clogged up.
That could cause all kinds of emission related things to trip.

 

[Cobraguy]

Sensor 1 Bank 1 is the upstream sensor on the right (passenger) side.

Lean code can be due to vacuum leaks, bad injectors, bad O2 sensor, just to name a few. So it's possible it's not actually lean.

Glowing cat is not good. That too can be caused by a lean condition, a rich condition, bad cat, just to name a few. Lean condition runs hot...rich condition can burn the leftover fuel inside the cat instead of the combustion chamber. I would have that checked asap. It's not necessarily tied to your O2 code...but possible. However, if the cat is bad, you should also be getting a code for poor cat efficiency. Since you're not, I would look carefully at other causes.

Edit: You know, if the O2 sensor is stuck lean, the ECM would try to enrichen that side...even though it didn't need it. That would cause an overly rich condition that could cause a glowing cat. See if you can't get a scan tool to monitor the O2 sensor cross counts and see what it's doing. Or if you have a lot of miles on the sensor, just go ahead and replace it anyway. They are wear items and should be replaced somewhere between 50K and 100K miles.

 

[nickorsi]

Thanks for all the replies. I had the codes pulled again this weekend at Autozone, the code pulled was P0430 " Catalyst Efficiency low-bank 2"

 

[Cobraguy]

That is for the left (driver's) side. It gets that reading off the downstream O2 sensor. That could be a bad cat or bad sensor.

 

[nickorsi]

My truck has about 198k miles on it, so I will probably try and replace the 02 sensor 1st and see if it solves the problem. I just need it to pass emissions and then I will be getting rid of it. Where is that O2 sensor located? Before or after the cat? Is it easily accessible?


Also forgot to mention this other code P0340- Cam sensor. can I just replace the sensor or do I need to replace the whole unit like I saw in other threads.

Thanks