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Diagnostic Procedure

NOTE: Fuel Pressure Gauge (J-34730-1A), Fuel Pressure Gauge Adapter (J-42242), Fuel Line Shut-Off Adapters (J-37287) and Fuel Line Shut-Off Quick Connect Adapters (J-37287-100) are required to perform this procedure. See Figure-Figure .

Clean fuel pipe connections, hose connections, and areas surrounding the connections before performing any disconnections in order to avoid possible contamination in the system.

  1. If diagnostic system check has already been performed, go to next step. If diagnostic system check has not been performed, go to DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 3.2L CTS article.
    2. NOTE: Inspect the fuel system for damage to the fuel system and external fuel leaks.
  2. Turn ignition ON, with engine OFF. Command the fuel pump ON using a scan tool. If fuel pump operates, go to next step. If fuel pump does not operate, go to FUEL PUMP ELECTRICAL CIRCUIT DIAGNOSIS .
  3. Observe the FUEL LEVEL SENSOR LEFT voltage using a scan tool. If fuel level sensor left voltage is less than 0.8 volt, go to next step. If fuel level sensor left voltage is greater than 0.8, volt go to step  6.
  4. Observe the FUEL LEVEL SENSOR RIGHT voltage using a scan tool. If fuel level sensor right voltage is less than 0.8 volt, go to next step. If fuel level sensor right voltage is greater than 0.8 volt, go to step  18.
  5. Add 5 gallons (19 liters) of fuel. Operate the vehicle within the conditions of the customer's concern. Monitor the fuel trim related parameters using a scan tool. If any of the scan tool parameters indicate a lean condition, go to step  20. If scan tool does not indicate any lean condition, see SYMPTOMS under TROUBLE SHOOTING - NO CODES - 3.2L CTS article.
    6. NOTE: Fuel pump may need to be commanded ON a few times in order to obtain the highest possible fuel pressure.
  6. Turn ignition OFF. Install the Fuel Pressure Gauge and Fuel Pressure Gauge Adapter. See Figure. Turn ignition ON, with engine OFF. Do not start the engine. Command fuel pump ON using a scan tool. Observe the fuel pressure gauge, while the fuel pump is operating. If fuel pressure is within 49-55 psi (337-379 kPa), go to next step. If fuel pressure in not within 49-55 psi (337-379kPa), go to step  13.
    7. NOTE: The fuel pressure will drop when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant.
  7. Allow fuel pressure to stabilize. Monitor the fuel pressure gauge for one minute. If fuel pressure decreases by more than 5 psi (34 kPa), go to step  10. If fuel pressure remains constant, go to next step.
  8. Relieve fuel pressure to 10 psi (69 kPa). Monitor fuel pressure gauge for 5 minutes. If fuel pressure decreases by more than 2 psi (14 kPa), go to step  26. If fuel pressure remains constant, go to next step.
  9. Operate vehicle within the conditions of the customer's concern. Monitor the fuel related parameters using a scan tool. If any of the scan tool parameters indicate a lean condition, go to step  20. If scan tool does not indicate any lean condition, see SYMPTOMS under TROUBLE SHOOTING - NO CODES - 3.2L CTS article.
  10. Turn ignition OFF. Remove vent hose from the fuel pressure regulator. Turn ignition ON, with engine OFF. Command fuel pump ON using a scan tool. Inspect for a fuel leak from the fuel pressure regulator atmospheric vent. If the fuel pressure regulator is leaking fuel, go to step  25. If fuel pressure regulator is not leaking fuel, go to next step.
  11. Perform the following:
    1. Turn OFF the ignition.
    2. Relieve the fuel pressure. See FUEL SYSTEM PRESSURE RELEASE .
    3. Disconnect the fuel feed hose and the fuel return hose from the fuel rail pipes. See FUEL LINE DISCONNECT FITTINGS under FUEL SYSTEMS in REMOVAL & INSTALLATION - CTS article.
    4. Install Fuel Line Shut-Off Adapters and Fuel Line Shut-Off Quick Connect Adapters between fuel hoses and the fuel rail pipes.
    5. Open the valves on the fuel pipe shut-off adapters.
    6. Turn ignition ON, with engine OFF.
    7. Command fuel pump ON using a scan tool.
    8. Bleed air from the fuel pressure gauge.
    9. Command fuel pump ON and then OFF using a scan tool.
    10. Close the fuel feed pipe shut-off valve.
    11. Monitor fuel pressure gauge for one minute.

    If fuel pressure remains constant, go to step  22. If fuel pressure does not remain constant, go to next step.

  12. Turn ignition OFF. Open the fuel feed pipe shut-off valve. Turn ignition ON, with engine OFF. Command fuel pump ON and OFF using a scan tool. Close the fuel return pipe shut-off valve. Monitor fuel pressure gauge for one minute. If the fuel pressure remains constant, go to step  25. If fuel pressure does not remain constant, go to step  23.
  13. Is the fuel pressure is more than 55 psi (379 kPa), go to step  15. If fuel pressure is less than 55 psi (379 kPa), go to next step.
  14. If the fuel pressure more than 0 psi (0 kPa), go to step  17. If fuel pressure is 0 psi (0 kPa), go to step  20.
  15. Perform the following:
    1. Turn ignition OFF.
    2. Relieve the fuel pressure. See FUEL SYSTEM PRESSURE RELEASE .
    3. Disconnect the fuel return hose from the fuel rail return pipe. See FUEL LINE DISCONNECT FITTINGS under FUEL SYSTEMS in REMOVAL & INSTALLATION - CTS article.
    4. Attach a length of flexible fuel hose to the fuel rail return pipe.
    5. Place the open end of the flexible fuel hose into an approved gasoline container.
    6. Turn ignition ON, with engine OFF.
    7. Observe fuel pressure gauge while the fuel pump is operating.

    If the fuel pressure is within 49-55 psi (337-379 kPa), go to step  24. If fuel pressure is not within 49-55 psi (337-379 kPa), go to next step.

  16. Inspect the fuel rail return pipe and fuel rail outlet passage for a restriction. Did you find and correct any restrictions? If yes, go to step  27. If fuel rail return pipe and fuel rail outlet passage are okay, go to step  25.
  17. Perform the following:
    1. Turn ignition OFF.
    2. Relieve the fuel pressure. See FUEL SYSTEM PRESSURE RELEASE .
    3. Disconnect the fuel return hose from the fuel rail return pipe. See FUEL LINE DISCONNECT FITTINGS under FUEL SYSTEMS in REMOVAL & INSTALLATION - CTS article.
    4. Install Fuel Line Shut-Off Adapters and Fuel Line Shut-Off Quick Connect Adapters between the fuel return pipe and the fuel rail.
    5. Open the valve in the fuel pipe shut-off adapter.
    6. Turn ignition ON, with engine OFF.
    7. Command fuel pump ON using a scan tool.
    8. Bleed air from the fuel system.
    9. Monitor Fuel Pressure Gauge.
      10. CAUTION: DO NOT allow fuel pressure to exceed 75 psi (517 kPa). Excessive pressure may damage the fuel system.
    10. Slowly close the Fuel Line Shut-Off Adapter valve, in the fuel return pipe.
    11. Command the fuel pump ON using a scan tool.
    If fuel pressure increases to more than 55 psi (379 kPa), go to step  25. If fuel pressure is less than 55 psi (379 kPa), go to step  20.
  18. Remove both fuel pump/sender assemblies. See FUEL PUMP/SENDER ASSEMBLY under FUEL SYSTEMS in REMOVAL & INSTALLATION - CTS article. Inspect the feed fuel pipe of the siphon jet pump for a restriction and the fuel strainer for contaminants. Did you find and correct any restrictions or contaminant conditions? If yes, go to step  27. If no restrictions or contaminants were found, go to next step.
  19. Inspect the fuel return pipe of the siphon jet pump for a restriction. Did you find and correct a restrictions on the fuel return pipe of the siphon jet pump? If yes, go to step  27. If no restrictions were found, go to step  26.
  20. Inspect the fuel filter and fuel feed pipe for a restriction. Did you find and correct a restriction in the fuel filter or fuel feed pipe? If yes, go to step  27. If no restrictions were found, go to next step.
  21. Inspect the fuel pump harness connectors and ground circuits for poor connections. Did you find and correct any poor connections? If yes, go to step  27. If no poor connections were found, go to next step.
  22. Remove the right fuel pump/sender assembly. See FUEL PUMP/SENDER ASSEMBLY under FUEL SYSTEMS in REMOVAL & INSTALLATION - CTS article. Inspect the fuel pump flex hose for damage and the in-tank fuel pump harness connectors for poor connections. Check the fuel strainer for a restriction and the fuel tank for contaminates. Did you find and correct the condition. If yes, go to step  27. If no, go to step  26.
  23. Turn ignition OFF. Raise the fuel rail, with the fuel lines connected. Turn ignition ON, with engine OFF. Command the fuel pump ON using a scan tool. Locate and replace the leaking fuel injector. See FUEL RAIL & INJECTORS under FUEL SYSTEMS in REMOVAL & INSTALLATION - CTS article. After repairs are complete, go to step  27.
  24. Locate and repair the restricted fuel return pipe. After repairs are complete, go to step  27.
    25. NOTE: Inspect for a missing or damaged fuel pressure regulator "O" ring seal before replacing the fuel pressure regulator.
  25. Replace fuel pressure regulator. See FUEL PRESSURE REGULATOR under FUEL SYSTEMS in REMOVAL & INSTALLATION - CTS article. After repairs are complete, go to step  27.
  26. Replace the right fuel pump/sender assembly. See FUEL PUMP/SENDER ASSEMBLY under FUEL SYSTEMS in REMOVAL & INSTALLATION - CTS article. After repairs are complete, go to step  27.
  27. Operate the system in order to verify the repair. If system operates properly, system is okay. If system does not operate properly, go to step  3.
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