LEMON Manuals: Even more car manuals for everyone
Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 258 (Engine Controls Self-Diagnostics - 2.2L) >> Diagnostic Tests >> DTC P0171: Fuel Trim System - Lean >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2003 GMC Sonoma and 2003 Chevrolet S10 Pickup. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
    2. NOTE: If any DTCs are set, other than DTC P0171, refer to affected DTCs before proceeding with this diagnosis. See DIAGNOSTIC TROUBLE CODE DEFINITIONS  .
  2. Install a scan tool. Review the Freeze Frame/Failure Records and record the displayed data for this DTC. Select Fuel Trim Data parameter. Start engine and observe the Fuel Trim Index. Does the scan tool indicate that the Fuel Trim Index is more than 20 percent? If yes, go to next step. If no, see DIAGNOSTIC AIDS  .
  3. Operate engine idle. Using scan tool, observe O2S parameters. 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 .
  4. Turn engine off. Check vacuum hoses for splits, kinks, and proper connections. Check for low fuel pressure. Repair as necessary. Did you find and correct the condition? If yes, go to step  8 . If no, go to step  7 .
  5. Turn engine off. Turn ignition on, with engine off. Observe the MAP sensor pressure parameter with a scan tool. The MAP sensor pressure should be within the range specified for your altitude. See SENSOR OPERATING RANGE CHARTS - TRUCKS article. Does the MAP indicate the correct barometric pressure? If yes, go to next step. If no, go to DTC P0105: MAP/TP SENSOR CIRCUIT - INSUFFICIENT ACTIVITY  .
  6. Turn ignition off. Inspect the O2S for proper installation, and connectors and wires are secured and not contacting the exhaust system. Test for a short between the O2S signal circuit and the low reference circuit. Inspect the following AIR system components for proper operation: The air pump, relay, check valve, hoses, and pipes. Did you find and correct the condition? If yes, go to step  8 . If no, diagnose fuel system.
  7. Operate engine at idle and check for missing, loose or leaking exhaust components. Check for vacuum leaks at intake manifold, throttle body and injector "O" rings. Check air induction system and air intake ducts for leaks. Check PCV for leaks. Did you find and correct the condition? If yes, go to next step. If no, check for a mechanical problem.
    8. NOTE: After repairs, use the scan tool Fuel Trim Reset function in order to reset the long term fuel trim.
  8. Use the scan tool in order to clear the DTCs. Turn ignition off for 30 seconds. Start engine. Operate the vehicle within the Conditions for Running the DTC. See CONDITIONS FOR RUNNING DTC  . Does the DTC run and pass? If yes, go to next step. If no, go to step  2 .
  9. Using scan tool, observe stored information and capture information. Does the scan tool display any DTCs that you have not diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS  . If no, system is okay.
scientia non olet · About LEMON Manuals