P129D

DTC P129D

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.

* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P129D

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Fuel Pump Driver Control Module Ignition 1 Switch Circuit Low Voltage

Diagnostic Fault Information






Circuit/System Description

The fuel pump flow control module (FPCM) monitors the IGN voltage circuit in order to determine if the voltage is within the normal operating range.

Conditions for Running the DTC

* The key is in Run or Crank.

* The engine is running.

Conditions for Setting the DTC

* The FPCM detects that the IGN voltage is less than 6.0 V.

* The above condition is present for 7 seconds.

Action Taken When the DTC Sets

DTC P129D is a Type B DTC.

Conditions for Clearing the DTC

DTC P129D is a Type B DTC.

Reference Information

Schematic Reference

Engine Controls Schematics (LS3) [1][2]Electrical DiagramsEngine Controls Schematics (LS7) [1][2]Electrical DiagramsEngine Controls Schematics (LS9) [1][2]Electrical Diagrams

Connector End View Reference

Component Connector End Views 5 Bow Lowered Switch (CM7)

Description and Operation

Fuel System Description (LS3 or LS7) Description and OperationFuel System Description (LS9) Description and Operation

Electrical Information Reference

* Circuit Testing Circuit Testing

* Connector Repairs Connector Repairs

* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections

* Wiring Repairs Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References Control Module References for scan tool information

Circuit/System Testing

1. Verify that DTC P0562 is not set.

• If DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.

2. Ignition OFF, disconnect the harness connectors at the FPCM, and X2 at the FPCM relay.

3. Connect a test lamp between the appropriate IGN voltage circuit terminals listed below and ground.

* FPCM terminal 15

* FPCM relay terminal 5

4. Ignition ON, verify the test lamp turns on.

• If the test lamp is OFF, test the IGN voltage circuit a short to ground or an open/high resistance.

5. Ignition OFF, connect the harness connector at the FPCM.

6. Connect a test lamp between the X2 FPCM relay harness connector terminal 5 and ground.

7. Ignition ON, verify the test lamp is ON.

• If the test lamp is OFF, test the IGN voltage circuit an open/high resistance. If the circuit tests normal, replace the FPCM.

8. If all circuits test normal, replace the FPCM relay.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.

* Fuel Pump Flow Control Module Replacement Fuel Pump Flow Control Module Replacement

* Fuel Pump Flow Control Module Relay Replacement Fuel Pump Flow Control Module Relay Replacement

* Control Module References Control Module References for FPCM replacement, setup, and programming