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HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 220 (ENGINE CONTROLS SELF-DIAGNOSTICS - 2.2L BI-FUEL)DIAGNOSTIC TESTSDTC P0005: HIGH PRESSURE LOCK-OFF SOLENOID CONTROL CIRCUITDIAGNOSTIC PROCEDURE
1999 GMC Forward Control 5.7 R, Automatic

Diagnostic Procedure

1999 GMC Forward Control 5.7 R, AutomaticSECTION Diagnostic Procedure
WARNING: This page is about a different car, the 2003 Chevrolet Cavalier. 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 (Alternative Fuels). If yes, go to next step. If no, go to DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS (ALTERNATIVE FUELS)  under SELF-DIAGNOSTIC SYSTEM.
  2. Turn ignition switch to RUN position, engine OFF. Command the HPL solenoid ON and OFF using a scan tool. Does the HPL solenoid respond to the scan tool commands? If yes, go to next step. If no, go to step  4.
  3. Observe the Freeze Frame/Failure Records for this DTC. Turn ignition switch to OFF position for 30 seconds. Turn ignition switch to RUN position, engine OFF. Operate the vehicle within the Conditions for Running the DTC. See CONDITIONS FOR RUNNING THE 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? If yes, go to next step. If no, see INTERMITTENTS in TROUBLE SHOOTING - 2.2L CAVALIER - BI-FUEL - CNG/GASOLINE article.
  4. Turn ignition switch to OFF position. Disconnect HPL solenoid harness connector. Turn ignition switch to RUN position, engine OFF. Probe the HPL solenoid ignition voltage circuit using a test light connected to a good ground. Does the test light illuminate? If yes, go to next step. If no, go to step  9.
  5. Connect a test light between the HPL solenoid control circuit and the HPL solenoid ignition voltage circuit. Command the HPL solenoid ON and OFF using a scan tool. Does the test light turn ON and OFF with each command? If yes, go to step  10. If no, go to next step.
  6. Does the test light remain illuminated with each command? If yes, go to step  8 If no, go to next step.
  7. Check the HPL solenoid control circuit for an open or for a short to voltage. Did you find and correct the condition? If yes, go to step  14. If no, go to step  11.
  8. Check the HPL solenoid control circuit for a short to ground. Did you find and correct the condition? If yes, go to step  14. If no, go to step  13.
  9. Repair the HPL solenoid ignition voltage circuit for an open or short to ground. After repair, go to step  14.
  10. Inspect for poor connections at the HPL solenoid. Did you find and correct the condition? If yes, go to step  14. If no, go to step  12.
  11. Inspect for poor connections at the PCM harness connector. Did you find and correct the condition? If yes, go to step  14. If no, go to step  13.
  12. Replace the HPL solenoid. After repair, go to step  14.
  13. Replace PCM. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL & INSTALLATION - CAVALIER & SUNFIRE article. Program PCM with correct vehicle software and calibration. After repair, go to next step.
  14. Observe the Freeze Frame/Failure Records for this DTC. Turn ignition switch to OFF position for 30 seconds. Turn ignition switch to RUN position, engine OFF. Operate the vehicle within the Conditions for Running the DTC. See CONDITIONS FOR RUNNING THE 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? If yes, go to step  2. If no, go to next step.
  15. Observe the CAPTURE INFO using a scan tool. Are there any DTCs that have not been diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay at this time.
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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.