Lack of heated upstream oxygen sensor, bank 1. Does upstream mean before the cat? I'm trying to pinpoint which one is bad. Thanks

 

DTC P1131 - lack of HO2S-11 switches, sensor indicates lean (bank 1, sensor 1). This is the upstream sensor on the passenger side cylinder bank before the cat. How many miles on the veh?. Possibly it is the sensor itself, but it might not be. You need to have someone go in and look at the actual data being provided by the sensor. O2 sensors "switch" from low volts (.1v) to high volts (1v) indicating the oxygen content of the exhaust. A sensor that is operating properly and is stuck "lean" or at a low voltage is indicating a high oxygen content in the exhaust. This could be the sign of a vacuum leak, or other things. My point is, just don't assume that it is the sensor that is bad (it could be). If you want to spend some money go ahead and replace it, if the DTC goes away, you've found the problem. If it doesn't, you'll have to look elsewhere.

 

rlh68050,
Thanks for the quick reply. Its a 2000 with 5.4L and 89,000 miles. I looked at the print out again and it is also throwing code P1132 and P0171 in addition to P1131.

 

The 1132 is the oppisite of the 1131. It is still for bank 1, sensor 1, but it is stuck rich. I would probably go ahead and change out the O2 sensor on that side and see if it goes away. Or if you really want to make sure it is the sensor, swap the right and left bank sensors, clear the codes, and see if the faults move to bank 2.

 

Excellent suggestion. Thanks!