P129C
DTC P129B or 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 Descriptors
DTC P129B
- Fuel Pump Driver Control Module System Voltage Low
DTC P129C
- Fuel Pump Driver Control Module System Voltage High
Diagnostic Fault Information
Circuit/System Description
The fuel pump power control module monitors the battery positive voltage circuit to verify the voltage is between the normal operating range. The DTC can set for a circuit or system voltage out of range.
Conditions for Running the DTC
P129B
* The engine is running.
* The ignition voltage is greater than 7 V.
* The fuel pump enable circuit is commanded ON.
* The DTC runs continuously when the conditions above are met.
P129C
* The engine is not running.
* The ignition voltage is greater than 7 V.
* The fuel pump enable circuit is commanded ON.
* The DTC runs continuously when the conditions above are met.
Conditions for Setting the DTC
P129B
The fuel pump power control module detects the battery positive voltage is less than 7 V for 1 s.
P129C
The fuel pump power control module detects the battery positive voltage is greater than 18 V for 1 s.
Action Taken When the DTC Sets
DTCs P129B and P129C are Type C DTCs.
Conditions for Clearing the DTC
DTCs P129B and P129C are Type C DTCs.
Reference Information
Schematic Reference
Engine Controls Schematics [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views Sunshade - Left
Description and Operation
Fuel System Description Fuel System Description
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Electrical Center Identification Views Fuse Block - Underhood Label
* 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 Verification
1. Ignition OFF.
2. Test for 12.4-12.8 V at the battery terminals and record the reading. The battery voltage should stabilize after a few minutes of turning the ignition OFF.
• If not between 12.4 V-12.8 V
Refer to Battery Inspection/Test Battery Inspection/Test.
• If between 12.4 V-12.8 V
3. Engine running, accessories OFF.
4. Test for 13.4-15 V at the battery terminals and record the reading.
• If not between 13.4-15 V
Refer to Charging System Test Component Tests and General Diagnostics.
• If between 13.4-15 V
5. Verify the engine control module scan tool Ignition 1 Signal voltage parameter is within 1 V of the battery voltage.
• If not within 1 V of the battery voltage
Refer to Circuit/System Testing.
• If within 1 V of the battery voltage
6. 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.
7. Verify the DTC does not set.
• If the DTC sets
Refer to Circuit/System Testing.
• If the DTC does not set
8. All OK.
Circuit/System Testing
1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the Fuel Pump Power Control Module. It may take up to 2 minutes for all vehicle systems to power down.
2. Test for less than 5 ohms between the ground circuit terminal 9 and ground.
• If 5 ohms or greater
1. Ignition OFF.
2. Test for less than 2 ohms in the ground circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, repair the open/high resistance in the ground connection.
• If less than 5 ohms
3. Verify a test lamp illuminates between the B+ circuit terminal 1 and ground.
• If the test lamp does not illuminate and the circuit fuse is good
1. Ignition OFF, remove the test lamp.
2. Test for less than 2 ohms in the B+ circuit end to end.
• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, verify the fuse is not open and there is voltage at the fuse.
• If the test lamp does not illuminate and the circuit fuse is open
1. Ignition OFF, remove the test lamp.
2. Test for infinite resistance between the B+ circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the Fuel Pump Power Control Module.
• If the test lamp illuminates
4. Replace the Fuel Pump Power Control Module.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
Fuel Pump Power Control Module Replacement Fuel Pump Power Control Module Replacement