P2635
DTC P2635 (Fuel Pump Control Module)
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 P2635
- Fuel Pump Flow Performance
Diagnostic Fault Information
Circuit/System Description
The Fuel Pump Flow Performance Diagnostic provides a means to detect degradation in the performance of an electronic return-less fuel system that may not be detectable by input and output component circuit diagnostics. It uses fuel pressure error, defined as desired fuel pressure minus estimated fuel pressure, as the basis for fault determination.
Conditions for Running the DTC
* DTC P018B, P018C, P018D, P1255 or P06A6 are not active.
* DTC P0641 has not failed this ignition cycle.
* Fuel pump control is enabled and the fuel pump control state is normal.
* The system voltage is greater than 11 V.
* The engine has been running for more than 30 seconds.
Conditions for Setting the DTC
This DTC sets when the FPCM detects a predetermined fuel pressure performance degradation between the desired fuel pressure and the current estimated fuel pressure.
Action Taken When the DTC Sets
DTC P2635 is a Type B DTC.
Conditions for Clearing the DTC
DTC P2635 is a Type B DTC.
Diagnostic Aids
Using the Failure Records data may help locate an intermittent condition. If you cannot duplicate the DTC, the information in the Failure Records can help determine how many miles since the DTC set. The Fail Counter and Pass Counter can help determine how many ignition cycles that the diagnostic test reported a pass and/or a fail.
On vehicles equipped with a high pressure mechanical pump on Direct Fuel Injection engines, the vehicle may continue to run even though the pump in the fuel tank is not operating.
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 Verification
Ignition ON, command the fuel pump ON and OFF using the scan tool ECM output control. The fuel pump should turn ON and OFF.
Circuit/System Testing
Note: Do not replace the fuel pump control module based on a history DTC P2635. The DTC P2635 may be stored but that does not indicate a failure of the fuel pump control module. Refer to Strategy Based Diagnosis Strategy Based Diagnosis for further history DTC diagnostics.
1. Verify that DTCs P018C or P018D, are not set.
• If the DTCs are set, refer to DTC P018B-P018D P018B.
2. Ignition OFF, disconnect the X469 harness connector at the LH fuel tank jumper.
3. Ignition OFF, connect a test lamp between the appropriate signal circuit terminal listed below and ground.
* LH fuel tank jumper terminal A
* LH fuel tank jumper terminal B
* LH fuel tank jumper terminal C
4. Ignition ON, command the fuel pump ON and OFF using a FPCM scan tool controls. The test lamp should turn ON and OFF, as commanded.
• If the test lamp is always ON, test circuit for a short to voltage. If the circuit tests normal, replace the FPCM relay.
• If the test lamp is always OFF, test circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the FPCM relay.
5. If all circuits test normal, perform the Fuel System Diagnosis. Refer to Fuel System Diagnosis (LS9) Fuel System DiagnosisFuel System Diagnosis (LS3 or LS7) Fuel System Diagnosis.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* Fuel Pump Flow Control Module Relay Replacement Fuel Pump Flow Control Module Relay Replacement
* Control Module References Control Module References for FPCM replacement, programming and setup