: o2 Sensor Help

06-02-04, 06:42 PM
A while back my car got a diagnostic code PC0139 current, I was told it was the o2 sensor in front of the cat which needed to be replaced. Lately my car has been running bad, it started out with some hesitation around 45-55 mph, now it hesitates when I am in park and when I put it in drive, and it is noticebly worse at any mph. I checked the codes again today and there are no codes. I have not got a chance to change the o2 sensor yet but I was wondering if the o2 sensor would cause this. Also if it is the o2 causing this where is a good place to get an oem replacement since I hear the bosche o2 sensors dont perform as well.

Here is what I was previously told about my error code, please let me know if this is correct. Thanks for any help.

There are 4 O2 sensors in the system. One on the left bank, one on the right bank, one immediately before the cat and one after the cat. Replace the one immediately before the cat. Some resources will say that there are two or even three O2's before the cat referring to the left bank and right bank O2 sensors as being "before the cat"...the real pre-cat O2 sensor that you are looking for is the one that is a few inches ahead of the cat in the pipe under the car. Use the OEM O2 sensor for compatibility with the OBD2 diagnostics."