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Home › Chevrolet › 2001 › Impala LS › Repair and Diagnosis › Engine Performance › System › Engine Control System Self-Diagnostics - 3.8L › Diagnostic Tests › DTC P0418: Secondary Air Injection Relay Control Circuit › 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. Turn ignition on, engine off. Using scan tool, command secondary Air Injection (AIR) pump and relay on and off. If relay turns on and off with each command, see DIAGNOSTIC AIDS . If relay does not turn on and off with each command, go to next step.
  3. Turn ignition off. Remove AIR relay. Turn ignition on, engine off. Using test light connected to ground, probe ignition 1 voltage circuit, coil side, of AIR relay. If test light is on, go to next step. If test light is off, go to step  12.
  4. Connect a test light between control circuit (Brown wire) of AIR relay connector and ignition 1 voltage circuit of AIR relay connector. Using scan tool, command AIR pump relay on and off. If test light turns on and off with each command, go to step  11. If test light does not turn on and off with each command, go to next step.
  5. If test light remains on with each command, go to step  7. If test light does not remain on with each command, go to next step.
  6. Check Brown wire between AIR relay and PCM for short to voltage or open. If problem was found, repair as necessary. After repairs, go to step  16. If problem was not found, go to step  11.
    7. NOTE: AIR pump may be damaged if control circuit is shorted to ground.
  7. Check Brown wire between AIR relay and PCM for short to ground. If problem was found, repair as necessary. After repairs, go to next step. If problem was not found, go to step  15.
  8. Install AIR relay. Turn ignition on, engine off. Using scan tool, command AIR relay on and off. If AIR pump turns on and off with each command, go to step  16. If AIR pump does not turn on and off with each command, go to next step.
  9. Check and replace AIR fuse as necessary. Disconnect AIR pump connector. Connect a test light between AIR pump connector terminals. Using scan tool, command AIR pump relay on and off. If test light turns on and off with each command, go to step  13. If test light does not turn on and off with each command, go to next step.
  10. Check AIR relay connector for poor connections. If problem was found, repair as necessary. After repairs, go to step  16. If problem was not found, go to step  14.
  11. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step  16. If problem was not found, go to step  15.
  12. Repair open or short to ground in ignition 1 voltage circuit. After repairs, go to step  16.
  13. Replace AIR pump. After repairs, go to step  16.
  14. Replace AIR relay. After repairs, go to step  16.
  15. Replace PCM. Program replacement PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  16. 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.
  17. 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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