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Home >> Chevrolet >> 2024 >> Tahoe Commercial, 4WD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 11 (Engine Controls And Fuel - 3.0L (Lm2) Diesel - Diagnostic Information And Procedures (4 Of 5)) >> Diagnostic Information and Procedures >> DTC P129F >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different variant/trim than selected.
  1. Ignition/Vehicle - Off
  2. Verify the condition does not exist: Fuel - Contaminated/Poor Quality - Refer to: Contaminants-in-Fuel Diagnosis
    • If a condition exists 

      Repair or replace as necessary

    • Go to next step: If no condition exists 
  3. Operate the vehicle under the following conditions: Various engine loads

    Verify the following parameters are within 200 RPM of each other:

    • Fuel Pump Speed Command
    • Fuel Pump Speed
    • If within 200 RPM of each other 
    1. Ignition Off
    2. Replace the component: K111 Fuel Pump Power Control Module
    3. Ignition - On/Vehicle - In Service Mode
    4. Perform the scan tool function: Clear DTCs
    5. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

      Verify DTC P129F is not set.

      • If the DTC sets - Refer to step 4
      • Go to next step: If the DTC does not set
    6. All OK.
    • Go to next step: If not within 200 RPM of each other 
  4. Ignition/Vehicle & All vehicle systems - Off
  5. Disconnect the electrical connector: A7 Fuel Tank Fuel Pump Module & K111 Fuel Pump Power Control Module

    Test for less than 2 ohms between the test points:

    • Control circuit terminal 8 @Control module harness & Terminal 1 @ Component harness
    • Control circuit terminal 9 @Control module harness & Terminal 2 @ Component harness
    • Control circuit terminal 24 @Control module harness & Terminal 3 @ Component harness
    • If 2 ohms or greater 

      Repair the open/high resistance in the circuit.

    • Go to next step: If less than 2 ohms 
  6. Test for infinite resistance between the test points:
    • Control circuit terminal 8 @Control module harness & Terminal 9 @ Component harness
    • Control circuit terminal 9 @Control module harness & Terminal 24 @ Component harness
    • Control circuit terminal 24 @Control module harness & Terminal 8 @ Component harness
    • If less than infinite resistance 

      Repair the short between the circuits.

    • Go to next step: If infinite resistance 
  7. Replace the component: A7 Fuel Tank Fuel Pump Module
  8. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

    Verify the DTC does not set.

    • If the DTC sets 

      Replace the component: K111 Fuel Pump Power Control Module

    • Go to next step: If the DTC does not set 
  9. All OK.
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