P1151 - Lack of HO2S-21 Switch, Sensor Indicates Lean
A Heated Exhaust Oxygen (HO2S) sensor indicating lean at the end of a test is trying to correct for an over-rich condition. The test fails when the fuel control system no longer detects switching for a calibrated amount of time.
Symptoms: You will likely not notice any drivability problems.
Causes: A code P1151 may mean that one or more of the following has happened:
Electrical:
Short to VPWR in the harness or HO2S
Water in the harness connector
Open/shorted HO2S circuit
Corrosion or poor mating terminals and wiring
Damaged HO2S
Damaged PCM
Fuel System:
Excessive fuel pressure
Leaking/contaminated fuel injectors
Leaking fuel pressure regulator
Low fuel pressure or running out of fuel
Vapor recovery system
Induction System:
Air leaks after the MAF
Vacuum Leaks
PCV system:
Improperly seated engine oil dipstick
EGR System:
Leaking gasket
Stuck EGR valve
Leaking diaphragm or EVR
Base Engine:
Oil overfill
Cam Timing
Cylinder compression
Exhaust leaks before or near the HO2S(s)
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