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.

The engine is running.

The FPCM detects that the battery voltage supplied to the FPDM is less than 9 V for 5 seconds.

DTC P129B is a type A DTC.

DTC P129B is a type A DTC.

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

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

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.

2. Ignition OFF, disconnect the harness connectors at the FPDM.
3. 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.

⇒	If greater than the specified range, test the ground circuit for an open/high resistance.

4. Verify that a test lamp illuminates between the B+ circuit terminal 3 X1 and ground.

⇒	If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

5. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 5 X2 and ground.

⇒	If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.

6. If all circuits test normal, replace the Fuel Pump Flow Control Module Relay.

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.