Contour Enthusiasts Group Archives Forums General Troubleshooting P1131 code after UIM/LIM rebuild. New O2 sensor?

I'm getting the P1131 code, fuel air metering (O2 sensor) CEL after a UIM/LIM rebuild. I cleared the code and it came back within 10 minutes. When I was replacing the rear valve cover gaskets, I disconnected the O2 sensor connector in order to maneuver the wire harness back more. When I reconnected it, I used some electric cleaner for the terminals. I am thinking that this could have caused the O2 sensor to malfunction. I checked everything else and all else is connected properly. Do I need a new O2 sensor?

Per TSB, some reasons are
P1131 - Lack of HO2S-11 Switch, Indicates Lean When an HO2S sensor indicates lean at the end of a test, the system is trying to correct for an over-lean condition. The code is set when the fuel control system no longer detects switching for a calibrated amount of time.

Electrical:
· Short to VPWR or VREF in harness or HO2S
· HO2S circuit shorted to Ground
· Water in harness connector
· Open circuit
· Corrosion or poor mating terminals and wiring
· Damaged HO2S
· Damaged PCM (other DTCs should be present)

Fuel System:
· Excessive fuel pressure (stuck fuel pressure regulator, restricted fuel return lines, etc.)
· Leaking/contaminated fuel injectors or fuel pressure regulator
· Low fuel pressure or running out of fuel (fuel pump concern, fuel supply line restrictions, low fuel level, etc.)
· Vapor recovery system (stuck VMV, etc.)

Induction System:
· MAF contamination
· Air leaks between MAF and throttle plate
· PCV system / Other vacuum leaks
· Improperly seated engine oil dipstick

EGR System:
· Leaking gasket
· Stuck EGR valve / Leaking diaphragm or EVR

Base Engine:
· Oil overfill
· Incorrect cylinder compression
· Exhaust leaks before or near the HO2S
· Secondary air stuck on

I suggest you check/wipe out the connectors first and then check for vacuum leaks at the gaskets. Did you put new gaskets for everything you took out? And did you torque everything back to specs?

Awesome info Tony, thanks. I found that my O2 sensor connector wasn't seated all the way in and my accordian tube was loose. Alls good now.