I have an engine code p0131 which is an upstream sensor bank 1 sensor 1.
The engine light goes on and off on the dash but the code still stored, i have reset it but code has come back. the truck has 86,000 so i think its the sensor. My question is how many upstream sensor are there and where do i find which one is bank 1 sensor 1 . Any info would be appreciated thanks
chris

 

I believe there is only one on an O3, upstream is before the cat converter, an exhaust leak before or shortly after the sensor could cause the code or other engine performance issues. My advice, given the milage, just change the sensor and see if it clears up. They are only like $40 at the dealer. A shop will charge $150 to give you there best GUESS at what it COULD be.