Oxygen Sensor Info Needed

[97Explorer5.0]

I have a 97 Explorer 5.0 w/ 81K miles. A few months ago the check engine light came on. I had the dealer diagnose the problem as "Bank #1 rear oxygen sensor, slow response. Reprogram PCM. Retest".

I object to paying $350 for this service and have chosen to perform the job myself. I've climbed under the vehicle and noticed one in front of and behind the catalytic converter, but I believe there are (2) additional sensors further upstream. Does anyone know which one I should change based on the above dealer diagnosis? Thanks in advance.

Jeff

 

[Robert]

You want to replace the O2 sensor that is after the catalytic converter, on the plumbing that comes from the passenger side of the engine. You have 4 sensors, two upstream (before cats) and two downstream (after cats). Two are on the driver's side plumbing (bank 2) and two are on the passenger side plumbing (bank 1).

 

[97Explorer5.0]

Thanks for the reply.

I noticed only (1) pipe on the passenger side containing the CAT with (2) O2 sensors attached per your description. Since my vehicle doesn't have dual exhaust, would I have a pipe on the driver side or am I just not looking hard enough? Thanks for your help!

 

[Alec]

You should of course have an exhaust manifold on each side of the motor. Each manifold will go to 2 inline cats, then the 2 lines come together into the muffler then out with a single tailpipe. The 2 parallel pipes with cats on them should be side by side.