I have a bank 1 sensor 2 P0138 code. I only see 1 pipe though underneath. The auto parts store is telling my I should have 4 sensors. on the 1 pipe, I see 1 sensor before and after the CAT. I don't see any other feeds into that main pipe. I have followed it up all the way to were it comes out of the engine.

Are there really 4 on this? Again, I only see 2.

Thanks in advance

 

There are only 2 sensors on this system, not 4. Essentially 1 bank only, not 2.

 

thank you mega-engr!! I replaced the sensor after the CAT. I have now driven it about 2-3 hours, much of it freeway. I expected the engine light to reset itself by now. I guess there is more wrong, not the 02. I have read online that the air intake/filter may need looked at any any wiring to/from the O2's. I will check that next. Anyone have any other insight? Sure wish a code was exact, and not a list of items to check.

 

I am not sure if the code will reset. Soft codes may reset, but a hard code will need to have it cleared. I would invest into a code reader which can clear codes if you plan on keeping your vehicle and attempting to fix anything yourself.

 

finally, after about 300 miles of driving over 5 days, the light reset on its own. on day 3 I also unhooked the batteries for about 30 minutes. That didn't reset it though. About 100 miles later and 2 days after disconnecting the batteries, it finally reset itself. I am not sure if the disconnecting helped or not. I am just glad the issue is resolved. thank you for those who posted!