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HOMESERVICE MANUALSCHEVROLET1997CHEVY EXPRESS G3500, VAN CARGO, 6.5 FREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 71 (ENGINE CONTROLS - TESTS W/CODES - 5.0L)DIAGNOSTIC TROUBLE CODESDTC P0171 - FUEL TRIM SYSTEM LEAN BANK 1DIAGNOSTIC PROCEDURES
1997 Chevrolet Chevy Express G3500, Van Cargo, 6.5 F

Diagnostic Procedures

1997 Chevrolet Chevy Express G3500, Van Cargo, 6.5 FSECTION Diagnostic Procedures
WARNING: This page is about a different car, the 1998 GMC Savana, 1998 Chevrolet Chevy Van, and 1998 Chevrolet Chevy Express. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK , then go to next step.
  2. Check for the following conditions:
    • Exhaust system for corrosion, loose or missing hardware.
    • HO2S is securely installed and pigtail is not contacting exhaust manifold or ignition wiring.
    • Vacuum hoses for splits, kinks and proper connections. Throttle body, intake manifold and EGR for vacuum leaks.
    • IAC, if a high or unsteady idle is being experienced.
    • Crankcase ventilation valve, spring and "O" ring for proper installation.
    • Fuel for excessive water, alcohol or other contaminants.
    • VCM and sensor ground are clean, tight and in proper locations.

    If a problem is found, go to step 8). If no problem is found, go to next step.

  3. Connect a fuel pressure gauge to fuel rail fitting. Turn ignition off for 10 seconds. Turn A/C off. Turn ignition on. Fuel pump should run for about 2 seconds. It may be necessary to cycle ignition on greater than once to obtain maximum pressure. Note pressure with pump running. On CSI models, pressure should be 60-66 psi (4.2-4.8 kg/cm2 ). On SFI models, pressure should be 56-62 psi (3.9-4.4 kg/cm2 ). On all models, when pump stops, pressure may slightly vary, but should hold steady. If pressure is as specified, go to next step. If pressure is not as specified, go to step 11).
  4. Start and idle engine at normal operating temperature. If pressure decreases by 3-10 psi (.2-.7 kg/cm2 ), go to next step. If pressure does not decrease by 3-10 psi (.2-.7 kg/cm2 ), go to step 11).
  5. Perform injector balance test. See I - SYSTEM/COMPONENT TESTS - 5.0L article. If a problem is found, go to step 9). If no problem is found, go to next step.
  6. Perform canister purge solenoid check. See I - SYSTEM/COMPONENT TESTS - 5.0L article. If a problem is found, go to next step. If no problem is found, see DIAGNOSTIC AIDS.
  7. Repair EVAP system. Install scan tool. Operate vehicle in closed loop while monitoring LT and ST fuel trim values. LT fuel trim value should decrease to less than 158. ST fuel trim value should decrease to less than 180. If values are as specified, go to step 10). If values are not as specified, see DIAGNOSTIC AIDS.
  8. Repair as necessary. Operate vehicle in closed loop while monitoring LT and ST fuel trim values. LT fuel trim value should decrease to less than 158. ST fuel trim value should decrease to less than 180. If fuel trim values are as specified, go to step 10). If fuel trim values are not as specified, go to step 3).
  9. Replace fuel injector. Operate vehicle in closed loop while monitoring LT and ST fuel trim values. LT fuel trim value should decrease to less than 158. ST fuel trim value should decrease to less than 180. If values are as specified, go to next step. If values are not as specified, go to step 6).
  10. Lean condition is not present. See H - TESTS W/O CODES - 5.0L article. Go to step 12).
  11. Diagnose fuel system. See F - BASIC TESTING - 5.0L article. After repairs, go to next step.
  12. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter this DTC. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2).
  13. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.