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HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 260 (ENGINE CONTROLS - SELF-DIAGNOSTICS)DIAGNOSTIC TESTSDTC P0412: SECONDARY AIR INJECTION RELAY CONTROL CIRCUITDIAGNOSTIC PROCEDURES
1999 GMC Forward Control 5.7 R, Automatic

Diagnostic Procedures

1999 GMC Forward Control 5.7 R, AutomaticSECTION Diagnostic Procedures
WARNING: This page is about a different car, the 2003 Cadillac Seville and 2003 Cadillac DeVille. However, it is still accessible from the selected car via links, so may be relevant.
  1. Did you perform the Diagnostic System Check-Engine Controls? If yes, go to next step. If no, see DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
  2. Are DTCs P0102, P0410, P0418, and P0443 set? If yes, go to next step. If no, go to step  4.
  3. Inspect for the following conditions:
    • Short to ground in the ignition 1 voltage circuit.
    • A shorted component that shares the IGN 1 fuse.

    Replace the IGN 1 fuse as necessary. Did you find and correct the condition? If yes, go to step  16.

  4. Turn ignition on, with engine off. Command the AIR vacuum solenoid valve on and off with a scan tool. Does the AIR solenoid valve turn on and off with each command? If yes, go to next step. If no, go to step  6.
  5. Review the Freeze Frame/Failure Records data for this DTC. Turn off the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions For Running DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Does the DTC reset? If yes, go to next step. If no, see INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM.
  6. Turn ignition off. Disconnect the AIR solenoid valve electrical connector. Turn ignition on, with engine off. Probe the AIR solenoid valve ignition 1 voltage supply circuit with the test light connected to a good ground. Does the test light illuminate? If yes, go to next step. If no, go to step  13.
  7. Connect a test light between the AIR solenoid valve control circuit and the AIR solenoid valve battery voltage supply circuit. Command the AIR vacuum solenoid valve on and off with a scan tool. Does the test light turn on and off with each command? If yes, go to step  11. If no, go to next step.
  8. Does the test light remain illuminated with each command? If yes, go to step  10. If no, go to next step.
  9. Test the AIR solenoid control circuit for a short to voltage an open or high resistance. Did you find and correct the condition? If yes, go to step  16. If no, go to step  12.
  10. Test the control circuit between the AIR solenoid valve and the PCM for a short to ground. Did you find and correct the condition? If yes, go to step  16. If no, go to step  15.
  11. Test for an intermittent and/or poor connections at the AIR vacuum solenoid. Did you find and correct the condition? If yes, go to step  16. If no, go to step  14.
  12. Test for an intermittent and/or poor connections at the PCM. Did you find and correct the condition? If yes, go to step  16. If no, go to step  15.
  13. Repair the open or high resistance in the ignition 1 voltage circuit. Did you complete the repair? If yes, go to step  16.
  14. Replace the secondary AIR vacuum control solenoid. See SECONDARY AIR VACUUM CONTROL SOLENOID under MOTORS & SOLENOIDS in REMOVAL & INSTALLATION - DEVILLE & SEVILLE article. Did you complete the replacement? If yes, go to step  16.
  15. Replace PCM. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL & INSTALLATION - DEVILLE & SEVILLE article. Did you complete the replacement? If yes, go to next step.
  16. Clear the DTCs with a scan tool. Turn off the ignition for 30 seconds. Start the engine and operate vehicle within the Conditions For Running DTC. You may also operate vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition cycle? If yes, go to step  2. If no, go to next step.
  17. Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, 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.