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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 51 (Engine Control System - Self-Diagnostics - 4.2L) >> Diagnostic Tests >> DTC P1171: Lean Exhaust Under Heavy Load >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2002 Oldsmobile Bravada, 2002 GMC Envoy XL, 2002 GMC Envoy, and 2002 Chevrolet TrailBlazer. 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, see DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
  2. Turn ON the ignition, with the engine OFF. Install a scan tool. Are any component related DTCs set? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS  . If no, go to next step.
  3. Observe the Freeze Frame/Failure Records data for this DTC. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running DTC as specified in the supporting test or as close to the Freeze Frame/Failure Records data that you observed. Does the DTC fail this ignition cycle? If yes, go to next step. If no, see DIAGNOSTIC AIDS  .
  4. Check the vehicle for an adequate amount of fuel. Add fuel to the vehicle's fuel tank if the fuel gauge is near empty. Was it necessary to add fuel? If yes, go to step  6 . If no, go to next step.
  5. Start the engine. Run the engine at normal operating temperature. Operate the engine above 1200 RPM. With a scan tool, observe the HO2S 1 voltage. Does the scan tool indicate HO2S 1 voltage varying outside 350-550 mV? If yes, diagnose fuel system. See appropriate BASIC DIAGNOSTIC PROCEDURES article. If no, see DTC P0134: HO2S CIRCUIT - INSUFFICIENT ACTIVITY - SENSOR 1  .
  6. Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running DTC. Does the DTC run and pass? If yes, go to next step. If no, go to step  2 .
  7. Observe the stored information, Capture Info with a scan tool. Does the scan tool display any DTCs that you have not diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS  . If no, system is okay.
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