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HOMESERVICE MANUALSCHEVROLET2001CHEVY EXPRESS G2500, VAN CARGO EXTENDED, 5.7 R, L31/KL8REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT VARIANT/TRIMSECTION 4 (ENGINE CONTROLS - SELF-DIAGNOSTICS - 4.3L)DIAGNOSTIC TESTSDTC P0418: AIR PUMP RELAY CONTROL CIRCUITDIAGNOSTIC PROCEDURES
2001 Chevrolet Chevy Express G2500, Van Cargo Extended, 5.7 R, L31/KL8

Diagnostic Procedures

2001 Chevrolet Chevy Express G2500, Van Cargo Extended, 5.7 R, L31/KL8SECTION Diagnostic Procedures
WARNING: This page is about a different variant/trim than selected.
  1. Perform powertrain diagnostic system check. See POWERTRAIN DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
  2. Turn ignition on, engine off. Using scan tool, command AIR pump relay on and off. If AIR pump relay turns on and off when commanded, go to next step. If AIR pump relay does not turn on and off when commanded, go to step  5.
    3. NOTE: Replace relay if DVOM goes to zero during current draw test.
  3. Turn ignition off. Disconnect PCM Red connector C2. Install fused jumper wire (5-amp) to PCM Red connector C2 terminal No. 36 (Brown wire). See Figure. Turn ignition on, engine off. Connect a DVOM, on 40-amp scale, between jumper wire and ground. Measure current from relay for 2 minutes. If current draw is less than 0.75 amp, see DIAGNOSTIC AIDS . If current draw is not less than 0.75 amp, go to next step.
  4. Turn ignition off. Disconnect AIR pump relay. AIR pump relay is located in right rear of engine compartment on "C" and "K" series and in underhood fuse block on "G" series. Measure resistance between PCM Red connector C2 terminal No. 36 (Brown wire) and ground. If resistance is infinite, go to step  12. If resistance is not infinite, go to step  10.
  5. Turn ignition off. Disconnect AIR pump relay. Connect a test light between Brown wire and Pink wire at AIR pump relay connector. Turn ignition on, engine off. Using scan tool, command AIR pump relay on and off. If test light turns on and off when commanded, go to step  8. If test light does not turn on and off with when commanded, go to next step.
  6. Using a test light connected to ground, probe Pink wire in AIR pump relay connector. If test light is on, go to next step. If test light is off, go to step  11.
  7. Turn ignition off. Reconnect AIR pump relay. Disconnect PCM Red connector C2. Turn ignition on, engine off. Using a fused jumper wire connected to ground, momentarily probe PCM Red connector C2 terminal No. 36 (Brown wire). If AIR pump relay turns on when circuit is grounded and off when circuit is opened, go to step  9. If AIR pump relay does not turn on when circuit is grounded and off when circuit is open, go to step  10.
  8. Check AIR pump relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step  14. If problem was not found, go to step  12.
  9. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step  14. If problem was not found, go to step  13.
  10. Repair Brown wire between AIR pump relay and PCM. After repairs, go to step  14.
  11. Repair Pink wire between AIR pump relay and underhood fuse/junction block. After repairs, go to step  14.
  12. Replace AIR pump relay. After repairs, go to step  14.
  13. Replace PCM. Program PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  14. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If DTC runs and passes, go to next step. If DTC does not run and pass, go to step  2.
  15. Using scan tool, observe stored information. If scan tool displays any DTCs that have not been diagnosed, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If scan tool does not display any DTCs, system is okay.
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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.