Hi, SES light went on so went to pull the codes and I got two codes P0138 and P0139. So I was wondering which O2 sensor it is in the diagram?
I have a 2000 Fed spec.



Oh, I also got a rotten egg smell, so is it the cat or pre cat? I might just get a y-pipe and a new hi-flow cat.

Thanks for the help.

 

Both codes you got are related to Bank1, Sensor 2 (downstream sensor), so it is obviously the rear sensor throwing the codes. One code is for slow response, the other is for high voltage, either of which could be triggered into a false reading by a faulty cat. So, if the cat is bad (that smell means ditch it before you're trying to find a fire extinguisher) replace it first, clear the codes, and see if they come back. FWIW, I had to change the rear sensor on my wife's 2000 maxima at about 40K, so it may be bad as well. Anyways, good luck man.

 

Thanks for the reply Grant. Wow, I didn't know a bad cat can cause a fire.