DTCs P0171, P0172, P0174 and P0175 indicate a problem when adaptive fuel strategy senses a lean or rich condition beyond the minimum or maximum calibrated limit. Possible causes for these faults are.
Fuel System
Excessive fuel pressure, leaking or contaminated fuel injectors, leaking fuel pressure regulator, low fuel pressure or engine running out of fuel or vapory recovery system fault.
Induction System
Air leaks after MAF sensor, air intake system obstructions, vacuum leaks, PCV system or improperly seated engine oil dipstick.
EGR System
Leaking gasket, stuck EGR valve or leaking diaphragm or EVR.
Engine Mechanical
Engine oil overfilled, cam timing, cylinder compression or exhaust leaks before or near HO2S.
Inspect engine for obvious defects in specified systems. Repair as necessary. If no faults are found, go to TEST DC, step 25).
20) DTC P1506: Check For Vacuum Leaks
This DTC indicates IAC system has reached over speed malfunction. Possible causes are.
IAC Circuit Short To Ground
IAC Assembly Stuck Open
Air Intake Leaks Or Restrictions
Damaged Throttle Body
Contaminated Or Damaged IAC Valve Assembly
Faulty Powertrain Control Module (PCM)
Start engine and allow to idle. Inspect air inlet system any of the following possible faults.
Cracked Or Punctured Air Inlet Tube
Loose Inlet Air Tube Or Air Cleaner Housing
Loose Or Damaged Throttle Body
Contaminated Or Damaged IAC Valve Assembly
Faulty EGR Valve Or Gasket
Faulty PCV Valve Or Hose
Check entire intake air system for vacuum leaks. Repair as necessary. If no vacuum leaks are found, go to next step.
NOTE:EVAP canister is also referred to as carbon canister.
Dec 17, 2008 at 9:32 AM
