Troublecode P1151 - Lack of H02s21 Switch -Sensor Indicates


CEL engine light is tripped, had autozone run the diagnostic and thats the code I recieved. Did a little research and below is what I found. Where do you suggest I start?

Diagnostic Trouble Codes (DTCs) P1131 bank (1) (Cylinder #1) and P1151 bank (2) indicate the fuel/air ratio is correcting rich for an overly lean condition. The HO2S voltage is less than 0.45 volt. DTCs P1132 bank (1) (Cylinder #1) and P1152 bank (2) indicate the fuel/air ratio is correcting lean for an overly rich condition. The HO2S voltage is greater than 0.45 volt.

DTCs P1130 and P1150 indicate the fuel control system has reached maximum compensation for a lean or rich condition and the HO2S is not switching.

DTC/HO2S Reference List

– HO2S-11 = DTCs P1131, P1132 and P1130

– HO2S-21 = DTCs P1151, P1152 and P1150

Possible causes:

Fuel system

– Excessive fuel pressure.
– Leaking fuel injector(s).
– Leaking fuel pressure regulator.
– Low fuel pressure.
– Contaminated injector(s)

Induction system

– Air leaks after the MAF.
– Vacuum leaks.
– Restricted air inlet.
– PCV system.
– Fuel purge system.
– Improperly seated dip stick.


– Leaking gasket.
– Stuck open EGR valve.
– Leaking diaphragm.

Base engine

– Oil overfill.
– Cam timing.
– Cylinder compression.
– Exhaust leaks before or near the HO2Ss.
l Check air intake for leaks, obstructions and damage.
l Check air filter, air filter housing for blockage.
l Verify integrity of the PCV system.
l Check for vacuum leaks.