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HOMESERVICE MANUALSCHEVROLET2000CHEVY EXPRESS G3500, VAN CARGO, 4.3 WREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMENGINE CONTROL SYSTEM SELF-DIAGNOSTICS - GASOLINE - 4.3L, 5.0L, 5.7L & 7.4LDIAGNOSTIC TESTSDTC P0171: FUEL TRIM SYSTEM LEAN - BANK 1DIAGNOSTIC PROCEDURES
2000 Chevrolet Chevy Express G3500, Van Cargo, 4.3 W

Diagnostic Procedures

2000 Chevrolet Chevy Express G3500, Van Cargo, 4.3 WSECTION Diagnostic Procedures
  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
    2. NOTE: If any DTCs other than DTC P0171 and P0174 are set, diagnose these first before proceeding.
  2. Start engine and let idle in closed loop. Using scan tool, monitor LONG TERM FT BN 1 display. If value is greater than 20 percent, go to step  4. If value is not greater than 20 percent, go to next step.
  3. Turn ignition on, with engine off. Using scan tool, read and record FAILURE RECORDS data. Turn ignition off for 15 seconds. Start engine and operate vehicle within conditions for this DTC to set, and as close to conditions noted in FAILURE RECORDS data as possible. Using scan tool, read SPECIFIC DTC while operating vehicle. Continue operating vehicle until DTC P0171 test runs. If scan tool displays DTC P0171 FAILED THIS IGN, go to next step. If scan tool does not display DTC P0171 FAILED THIS IGN, see DIAGNOSTIC AIDS .
  4. If DTC P0174 is also set, go to next step. If DTC P0174 is not set, go to step  6.
  5. Check exhaust system for leaks, restriction in fuel filter, and vacuum leaks in air induction system after MAF sensor. Check vacuum hoses for splits, kinks and proper routing. Check throttle body, intake manifold, and EGR valve for vacuum leaks. Check IAC, if high or unsteady idle condition exists. Check crankcase ventilation valve, spring and "O" ring for proper installation. Check AIR system for proper operation (if equipped). Check for fuel contamination. Check for good VCM and sensor grounds. If any of these items isolate problem or require repair, go to step  10. If all items are okay, go to step  7.
  6. Check exhaust system for leaks at bank 1. Check bank 1 HO2S 1 for proper installation. Ensure HO2S 1 harness and connector are not contacting exhaust system or secondary ignition wires. Check for vacuum leaks that may effect bank 1 HO2S 1. If any of these items isolate problem or require repair, go to step  10. If all items are okay, go to next step.
  7. 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 more 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 55-60 psi (3.9-4.2 kg/cm2 ). On all models, when pump stops, pressure may vary slightly, but should hold steady. If pressure is as specified, go to next step. If pressure is not as specified, go to step  13.
  8. Start engine. Allow engine to idle at normal operating temperature. If fuel pressure is 55-60 psi (3.9-4.2 kg/cm2 ), go to next step. If fuel pressure is not as specified, go to step  13.
  9. Perform injector balance test. See appropriate SYSTEM & COMPONENT TESTING article. If a problem is found, go to step  11. If no problem is found, go to step  14.
  10. Repair components as necessary. Using scan tool, reset fuel trim. Operate vehicle in closed loop while monitoring LONG TERM FT BN 1 display. If value decreases to less than 20 percent, go to step  12. If value does not decrease to less than 20 percent, go to step  7.
  11. Replace faulty fuel injector. Using scan tool, reset fuel trim. Operate vehicle in closed loop while monitoring LONG TERM FT BN 1 display. If value decreases to less than 20 percent, go to next step. If value does not decrease to less than 20 percent, go to step  7.
  12. Lean condition is not present at this time. If driveability symptoms are still present, see appropriate TROUBLE SHOOTING - NO CODES article. If no driveability symptoms are present, go to step  14.
  13. Diagnose fuel system. See appropriate BASIC DIAGNOSTIC PROCEDURES article. After repairs, go to next step.
  14. Using scan tool, clear DTCs. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, and 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, go to step  2.
  15. Using scan tool, select CAPTURE INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, go to applicable DTC test. If no undiagnosed DTCs are displayed, system is okay.
RENDER: 1.0x

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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.