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Tahoe / Yukon Service Manual

DTC P129F

Engine Controls and Fuel - 3.0L LM2 Diesel | Diagnostic Information and Procedures | Document ID: 5501057 Diagnostic Instructions Perform the Diagnostic System Check prior to using this diagnostic procedure: Diagnostic System Check - Vehicle Review the description of Strategy Based Diagnosis: Strategy Based Diagnosis An overview of each diagnostic category can be found here: Diagnostic Procedure Instructions DTC Descriptor DTC P129F Fuel Pump Power Control Module Fuel Pump Speed Signal Incorrect Circuit/System Description For an overview of the component/system, refer to: Fuel System Description

Component Description
A7 Fuel Tank Fuel Pump Module The component has a 3-phase motor. The control module converts the DC voltage from the battery to 3-phase AC to power the motor.
K111 Fuel Pump Power Control Module The control module contains a microprocessor used to process input data to control outputs. The control module communicates with the engine control module via serial data.

Conditions for Running the DTC DTC P1029, P102A, P102B, P1255, P12A6, U18A2 = Not set Ignition and Start Signal = Greater than 9 V Sensor Supply Voltage Command = On Conditions for Setting the DTC Fuel Pump Speed Command ≠ Fuel Pump Speed — For greater than 1 s Actions Taken When the DTC Sets DTCs listed in the DTC Descriptor category = Type B DTC Conditions for Clearing the DTC DTCs listed in the DTC Descriptor category = Type B DTC Reference Information Schematic Reference Engine Controls Schematics Connector End View Reference Master Electrical Component List Electrical Information Reference Circuit Testing Connector Repairs Testing for Intermittent Conditions and Poor Connections Wiring Repairs DTC Type Reference Powertrain Diagnostic Trouble Code (DTC) Type Definitions Scan Tool Reference Control Module References Circuit/System Verification

  1. Ignition » On / Vehicle » In Service Mode
  2. Verify DTC P0627, P0628, P0629, P1029, P102A, P102B, P1255, P12A6, P16D7, P16D8, U18A2 is not set. ⇒ If any of the DTCs are set Refer to: Diagnostic Trouble Code (DTC) List - Vehicle. ⇓ If none of the DTCs are set
  3. Perform the scan tool function: Clear DTCs
  4. 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 and no other DTCs are set. ⇒ If any other DTCs are set Refer to: Diagnostic Trouble Code (DTC) List - Vehicle. ⇒ If only DTC P129F is set Refer to: Circuit/System Testing ⇓ If no DTC is set
  5. All OK. Circuit/System Testing
  6. Ignition/Vehicle » Off
  7. 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 ⇓ If no condition exists
  8. 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 3.1. Ignition Off 3.2. Replace the component: K111 Fuel Pump Power Control Module 3.3. Ignition » On / Vehicle » In Service Mode 3.4. Perform the scan tool function: Clear DTCs 3.5. 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 3 ⇓ If the DTC does not set 3.6. All OK. ⇓ If not within 200 RPM of each other
  9. Ignition/Vehicle & All vehicle systems » Off
  10. Disconnect the electrical connector: A7 Fuel Tank Fuel Pump Module & K111 Fuel Pump Power Control Module Test for less than 2 Ω 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 Ω or greater Repair the open/high resistance in the circuit. ⇓ If less than 2 Ω
  11. 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. ⇓ If infinite resistance
  12. Replace the component: A7 Fuel Tank Fuel Pump Module
  13. 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 ⇓ If the DTC does not set
  14. All OK. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair: Diagnostic Repair Verification Fuel Tank Fuel Pump Module Replacement — A7 Fuel Tank Fuel Pump Module For control module replacement, programming, and setup refer to: Control Module References