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Home >> GMC >> 2001 >> Jimmy 4D Utility, 4WD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls Self-Diagnostics - 4.3L >> Diagnostic Tests >> DTC P0418: Secondary Air Injection Pump & Air Solenoid Circuit ("S" & "T" Series) >> Diagnostic Procedures

Diagnostic Procedures

  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. Using scan tool, command the relay on and off. If relay turns on and off when commanded, go to next step. If relay does not turn on and off when commanded, go to step  5.
  3. Turn ignition off. Disconnect PCM harness connector C2. Install 5-amp fused jumper wire to control circuit at PCM harness connector. Turn ignition on, with engine off. Replace relay if DVOM goes to zero during the current draw test. Using DVOM, check current draw from relay control circuit in PCM harness connector to ground for 2 minutes. If current draw measures less than 0.75 amps, see DIAGNOSTIC AIDS . If current draw does not measure less than 0.75 amps, go to next step.
  4. Turn ignition off. Disconnect AIR pump relay. Check resistance from the relay control circuit in PCM harness connector to ground. If resistance is infinite resistance, go to step  12. If resistance is not infinite, go to step  10.
  5. Turn ignition off. Disconnect relay. Connect test light between AIR pump relay control circuit and AIR pump relay ignition feed circuit, on coil side of the relay, at AIR pump relay harness connector. Turn ignition on, with engine off. Using scan tool, command 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 when commanded, go to next step.
  6. Using test light connected to ground, probe ignition feed circuit, located on coil side of relay, at AIR pump relay harness connector. If test light illuminated, go to next step. If test light does not illuminate, go to step  11.
  7. Turn ignition off. Reconnect relay. Disconnect PCM connector C2. Turn ignition on, with engine off. Using a fused jumper wire connected to ground, momentarily probe relay control circuit in PCM harness connector. If relay turns on when circuit is grounded and turns off when circuit is opened, go to step  9. If relay does not turn on when circuit is grounded and or turn off when circuit is opened, go to step  10.
  8. Check connections at relay. Repair as necessary. After repairs, go to step  14. If connections are okay, go to step  12.
  9. Check connections at PCM. Repair as necessary. After repairs, go to step  14. If connections are okay, go to step  13.
  10. Repair faulty relay control circuit. After repairs, go to step  14.
  11. Repair faulty relay ignition feed circuit. After repairs, go to step  14.
  12. Replace the relay. After replacing relay, go to step  14.
  13. Replace PCM. Perform PCM relearn procedure. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After replacing PCM, go to next step.
  14. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start and operate vehicle within the conditions for running the DTC. See CODE ENABLE CRITERIA . If DTC runs and passes, go to next step. If DTC resets, go to step  2.
  15. Using scan tool review the stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no DTCs are displayed, system is okay.
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