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Home >> Chevrolet >> 2024 >> Tahoe Commercial, 4WD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 9 (Engine Controls And Fuel - 3.0L (Lm2) Diesel - Diagnostic Information And Procedures (3 Of 5)) >> Diagnostic Information and Procedures >> DTC P1089 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different variant/trim than selected.
  1. Ignition/Vehicle - Off
  2. Verify the following conditions do not exist:
    • If a condition exists 

      Repair or replace as necessary

    • Go to next step: If no condition exists 
  3. Engine - Idling
  4. Verify the scan tool parameter: Fuel Pressure Sensor = 370 to 450 kPa (54 to 65 PSI)
    • Go to next step: If between 370 and 450 kPa (54 and 65 PSI) 
  5. Perform the following procedure/test: Cylinder Power Balance Test

    Verify the procedure/test passes.

    • If the procedure/test does not pass 

      Replace the component that failed the test: Q17 Fuel Injector

    • Go to next step: If the procedure/test passes 
    6. NOTE:

    Scan Tool Device Control: Fuel Pressure Control - Regulator 1 - Controls the following components:

    • Q18A Fuel Pressure Regulator 1
    • Q18C Fuel Pressure Regulator 3
  6. Perform the scan tool control function: Fuel Pressure Control - Regulator 1 - Increase & Decrease

    Verify the scan tool parameter: Fuel Rail Pressure Sensor = The value should change with each command.

    • If the value does not change 

      Replace the component: G18 Fuel Pump - High Pressure

    • Go to next step: If the value changes 
  7. Perform the scan tool control function: Fuel Pressure Control - Regulator 2 - Increase & Decrease

    Verify the scan tool parameter: Fuel Rail Pressure Sensor = The value should change with each command.

    • If the value does not change 

      Replace the component: Q18B Fuel Pressure Regulator 2

    • Go to next step: If the value changes 
  8. Ignition/Vehicle - Off
    9. NOTE:
    • In order to perform step 9 - 12, the fuel temperature must be greater than 10°C (50°F) or misdiagnosis may occur.
    • Leave the electrical connector connected.
  9. Disconnect the component: Fuel Return Hose @ Q18B Fuel Pressure Regulator 2 & Plug the fuel return hose(s) in order to prevent leakage.
  10. Install suitable hose to the component: Outlet @ Q18B Fuel Pressure Regulator 2 & Place the other end of the hose into a suitable container.
  11. Engine - Idling - Until air is purged from the hose
  12. Engine - Idling - For 15 s

    Verify the container contains less than 15 mL (0.5 US fl oz)

    • If 15 mL (0.5 US fl oz) or greater 

      Replace the component: Q18B Fuel Pressure Regulator 2

    • Go to next step: If less than 15 mL (0.5 US fl oz) 
  13. Ignition/Vehicle - Off
  14. Install the component: Fuel Return Hose @ Q18B Fuel Pressure Regulator 2
  15. Disconnect the electrical connector: Q17 Fuel Injector - All
  16. Disconnect the component: Fuel Injection Fuel Return Pipe @ Q17 Fuel Injector - All - Refer to: Fuel Injector Fuel Return Pipe Replacement

    Plug the fuel return hose(s) in order to prevent leakage.@Diesel Fuel Separator & Fuel Rail

    17. NOTE:

    Do NOT use the following tool or the incorrect test results will occur: Remote Start Switch

  17. Engine - Cranking - For 15 s
  18. Verify the condition does not exist: Leaking @ Q17 Fuel Injector
    • If a condition exists 

      Replace the appropriate component: Q17 Fuel Injector

    • Go to next step: If no condition exists 
  19. Ignition/Vehicle - Off
  20. Install the component: Fuel Injection Fuel Return Pipe
    21. NOTE:

    Perform the following test for all 6 components. - One at a time

  21. Perform the following steps:
    1. Disconnect the electrical connector: Q17 Fuel Injector - All
    2. Remove the component: F5BA Fuse@X50B Battery Distribution Engine Compartment Fuse Block
    3. Disconnect the electrical connector: E12 Glow Plug
      4. NOTE:

      The component must be discarded whenever removed and replaced with a NEW component:

    4. Remove the component: E12 Glow Plug - One at a time
    5. Place and hold a clean shop towel over the component: Threaded Hole @ Cylinder Head - Glow Plug
    6. Engine - Cranking - For 6 s

      Verify the condition does not exist: Fuel @ Shop Towel

    • If a condition exists 

      Replace the appropriate component: Q17 Fuel Injector

    • Go to next step: If no condition exists 
  22. Test or replace the component: G18 Fuel Pump - High Pressure
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