H41 DTCs P0172, P0174, P0171 AND P0175: FUEL SYSTEM AT THE CORRECTED FUEL TRIM
Diagnostic Trouble Codes (DTCs) P0171 bank 1 (Cylinder 1) and DTC
P0174 bank 2 indicate the fuel/air ratio is too lean. The fuel trim system is at the rich correction limit.
P0172 bank 1 and DTC
P0175 bank 2 indicate the fuel/air ratio is too rich. The fuel trim system is at the lean correction limit.
HO2S-11 = DTCs P0171 and P0172
HO2S-21 = DTCs P0174 and P0175
Excessive fuel pressure.
Leaking fuel injector(s).
Leaking fuel pressure regulator.
Low fuel pressure or running out of fuel.
Contaminated fuel injector(s).
Vapor management valve (VMV
Air leaks after the MAF
Vacuum leaks (vacuum lines and gaskets).
Restricted air inlet.
Fuel purge system.
Improperly seated engine oil dipstick.
Stuck open EGR
Exhaust leaks before or near the HO2S
Check intake air system for leaks, obstructions and damage.
Check air cleaner element, air cleaner housing for blockage.
Verify integrity of the PCV
Check for vacuum leaks.