LEMON Manuals: Even more car manuals for everyone
Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 330 (Engine Controls - Self-Diagnostics - 3.0L) >> Diagnostic Tests >> DTC P0171 Or P0174: Fuel Trim System - Lean >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2003 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
  1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, go to DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS .
    2. NOTE: If any DTCs are set other than DTC P0171 or P0174, diagnose affected DTC(s) before continuing with test. Refer to DIAGNOSTIC TROUBLE CODE DEFINITIONS .
  2. Install scan tool. Start engine. Operate vehicle within the Conditions for Running the DTC. See CONDITIONS FOR RUNNING DTC . Record the LT FT Cruise/Accel and LT FT Idle/Decel parameter values. Turn engine off. Turn ignition on, with engine off. Review the Freeze Frame/Failure Records and record displayed data for this DTC. Does the scan tool indicate that the LT FT Cruise/Accel parameter is more than 23 percent? If yes, go to step  4. If no, go to next step.
  3. Does the scan tool indicate that the LT FT Idle/Decel parameter is more than 8.1 percent? If yes, go to next step. If no, go to DIAGNOSTIC AIDS .
  4. Operate engine at idle. Observe the front HO2S parameters with a scan tool. Does the scan tool indicate that the values are within 200-800 mV and fluctuating? If yes, go to next step. If no, go to step  6.
  5. Turn engine off. Visually and physically inspect vacuum hoses for splits, kinks, and proper connections. Ensure that the vehicle has sufficient fuel. If fuel pressure is too low, this DTC may set. Did you find and correct the condition? If yes, go to step  8. If no, go to step  7.
  6. Turn engine off. Inspect the HO2S for proper installation. Verify that the electrical connectors and wires are secured and are not contacting the exhaust system. Did you find and correct the condition? If yes, go to step  8. If no, diagnose fuel system. Refer to FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 2.2L & 3.0L VUE article.
  7. Operate the engine at idle. Inspect for missing, loose, or leaking exhaust components. Inspect for vacuum leaks at the intake manifold and injector "O" rings, air induction system and air intake ducts for vacuum leaks, or crankcase ventilation system for leaks. Check for a skewed MAF sensor. Did you find and correct the condition? If yes, go to next step. If no, diagnose for an engine mechanical problem.
    8. NOTE: After repairs, reset the Long Term fuel with the scan tool Fuel Trim Reset function.
  8. Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start engine. Operate vehicle within the Conditions for Running the DTC. See CONDITIONS FOR RUNNING DTC . You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition? If yes, go to step  2. If no, go to next step.
  9. Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? If yes, diagnose affected DTC(s). See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no DTCs are displayed, system is okay.
scientia non olet · About LEMON Manuals