Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
DTC Descriptor
DTC P129B: System Voltage Low - FPDMDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
IGN/B+ | P129B | P129B | -- | -- |
Ground | -- | P129B | -- | -- |
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 engine is running.
Conditions for Setting the DTC
The FPCM detects that the battery voltage supplied to the FPDM is less than 9 V for 5 seconds.
Action Taken When the DTC Sets
DTC P129B is a type A DTC.
Conditions for Clearing the DTC
DTC P129B is a type A DTC.
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Charging System Description and Operation
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Testing
- 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.
- Ignition OFF, disconnect the harness connectors at the FPDM.
- Ignition OFF and scan tool disconnected, open and close the driver door, and wait 1 minute. Test for less than 5 Ω between the ground circuit terminal 5 X1 and ground.
- Verify that a test lamp illuminates between the B+ circuit terminal 3 X1 and ground.
- Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 5 X2 and ground.
- If all circuits test normal, replace the Fuel Pump Flow Control Module Relay.
| ⇒ | If not within the specified range, refer to Charging System Test. |
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| ⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. |
| ⇒ | If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Refer to Fuel Pump Flow Control Module Relay Replacement for Fuel Pump Flow Control Module Relay.
