P129C

DTC P129C

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 P129C
- System Voltage High - FPDM

Diagnostic Fault Information





Circuit/System Description

The fuel pump control module (FPCM) monitors the system voltage supplied to the fuel pump driver module (FPDM) to ensure that the voltage stays within the proper range. Damage to components, and incorrect data may occur when the voltage is out of range.

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC

The FPCM detects that the system voltage is greater than 18 V for 5 seconds.

Action Taken When the DTC Sets

DTC P129C is a type A DTC.

Conditions for Clearing the DTC

DTC P129C is a type A DTC.

Diagnostic Aids

* A high voltage DTC in multiple modules indicates a concern in the charging system.
* This DTC could be set by overcharging with a battery charger or jump starting.

Reference Information
Schematic Reference

Engine Controls Schematics (LS3) ([1][2]Electrical Diagrams) Engine Controls Schematics (LS7) ([1][2]Electrical Diagrams) Engine Controls Schematics (LS9) ([1][2]Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Charging System Description and Operation (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 (Programming and Relearning) for scan tool information

Circuit/System Verification

1. Engine running, accessories OFF, measure and record the battery voltage at the battery terminals. The voltage should be between 12.6 and 15.0 V.

• If not within the specified range, refer to Charging System Test (Charging System Test).

2. If all circuits test normal, replace the FPDM.

Repair Instructions

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

Refer to Fuel Pump Flow Control Module Relay Replacement (Service and Repair) for Fuel Pump Flow Control Module Relay.