SYS.OK|MANUAL.DB● LIVE
HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 260 (ENGINE CONTROLS - SELF-DIAGNOSTICS)DIAGNOSTIC TESTSDTC P0418: SECONDARY AIR INJECTION PUMP 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, P0412, and P0443 set? If yes, go to next step. If no, go to step  4.
  3. Test the ignition 1 voltage circuit for a short to ground. Replace the IGN 1 fuse as necessary. Did you find and correct the condition? If yes, go to step  18. If no, go to step  14.
  4. Install a scan tool. Turn ignition on, with engine off. Command the AIR pump relay ON and OFF with a scan tool. Does the AIR pump relay 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. Did the DTC fail this ignition cycle? If yes, go to next step. If no, see INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM.
  6. Turn ignition off. Remove the AIR pump relay. Turn ignition on, with engine off. Probe the AIR pump relay ignition 1 voltage circuit with a 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 control circuit of the AIR pump relay and the ignition 1 voltage circuit of the AIR pump relay. Command the AIR pump relay 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. NOTE: A short to voltage on the control circuit will allow the AIR pump to run continuously with the key in the OFF position.
  9. Test the AIR pump relay control circuit for an open or short to voltage. Did you find and correct the condition? If yes, go to step  17. If no, go to step  12.
    10. NOTE: A short to ground on the control circuit will allow the AIR pump to run continuously with the ignition key in the ON position.
  10. Test the AIR pump relay control circuit for a short to ground. Did you find and correct the condition? If yes, go to step  17. If no, go to step  16.
  11. Test for an intermittent and/or poor connections at the AIR pump relay. Did you find and correct the condition? If yes, go to step  18. If no, go to step  15.
  12. Test for an intermittent and/or poor connections at the PCM. Did you find and correct the condition? If yes, go to step  18. If no, go to step  16.
  13. Repair the open or high resistance in the AIR pump relay ignition 1 voltage circuit. Did you complete the repair? If yes, go to step  18.
  14. Repair the short to ground in the circuits that share the IGN 1 fuse or the shorted component on the same circuit. Did you complete the repair? If yes, go to step  18.
  15. Replace the AIR pump relay. Did you complete the replacement? If yes, go to step  18.
  16. 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.
  17. Ensure all components are installed and secured properly. Ensure all connections are complete and secured. Command the AIR pump relay on with a scan tool. Does the AIR pump turn on when commanded with a scan tool? If yes, go to next step. If no, go to step  2.
  18. 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.
  19. 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.
RENDER: 1.0x

NO RELATED

Recommended Tools & Savings

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Affiliate disclosure: We may earn a commission at no extra cost to you.

Shop Manual-Ready ToolsFree Quote CheckQuote Shield Pro

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.