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 engine control module (ECM) supplies voltage to the fuel pump control module when the ECM detects that the ignition is on. The voltage from the ECM to the fuel pump control module remains active for 2 seconds, unless the engine is in crank or run. While this voltage is being received, the fuel pump control module closes the ground switch of the fuel pump and also supplies a varying voltage to the fuel tank pump module in order to maintain the desired fuel rail pressure.
Conditions for Running the DTC
* DTC P018B, P018C, P018D, P0231, P0232, P023F, P064A, 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 fuel pump control module detects a predetermined fuel pressure performance degradation between the desired fuel rail pressure and the current fuel rail 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.
Reference Information
Schematic Reference
Engine Controls Schematics (except L96) ([1][2]Electrical Diagrams)Engine Controls Schematics (L96) ([1][2]Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
Description and Operation
Fuel System Description (Fuel System Description)
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 Testing
1. Verify that DTCs P018C, P018D, P0231, P0232, or P023F are not set.
• If the DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle (Diagnostic Trouble Code (DTC) List - Vehicle).
2. Ignition OFF, disconnect the harness connector at the G12 fuel pump.
3. Ignition OFF, test for less than 5.0 ohm between the G12 fuel pump low reference circuit terminal A and ground.
• If greater than the specified range, test the G12 fuel pump low reference circuit for a high resistance. If the circuit tests normal, replace the K27 fuel pump control module.
4. Ignition OFF, install a test lamp between the control circuit terminal D and the low reference circuit terminal A.
5. Ignition ON, command the Fuel Pump Relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
• If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the K27 fuel pump control module.
• If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K27 fuel pump control module.
6. Perform the Fuel System Diagnosis (Without FPCM) (Testing and Inspection)Fuel System Diagnosis (FPCM) (Component Tests and General Diagnostics) to verify proper fuel pressure.
• If the fuel pressure is not normal, replace the G12 fuel pump
7. If all circuits test normal, replace the K27 fuel pump control module.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Fuel Tank Fuel Pump Module Replacement (15 Reg Cab With 26 Gal Tank) (Fuel Tank Fuel Pump Module Replacement (15 Reg Cab With 26 Gal Tank))Fuel Tank Fuel Pump Module Replacement (15 Ext/Crew Cab With 26 Gal Tank) (Fuel Tank Fuel Pump Module Replacement (15 Ext/Crew Cab With 26 Gal Tank))Fuel Tank Fuel Pump Module Replacement (15 Reg/Ext/Crew Cab w/34 Gal Tank) (Fuel Tank Fuel Pump Module Replacement (15 Reg/Ext/Crew Cab w/34 Gal Tank))Fuel Tank Fuel Pump Module Replacement (25/35 Series) (Fuel Tank Fuel Pump Module Replacement (25/35 Series))
* Control Module References (Control Module References) for fuel pump control module replacement, setup, and programming