For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle

• | Review Strategy Based Diagnosis

• | Diagnostic Procedure Instructions

### DTC Descriptor

DTC P2635: Fuel Pump Flow Performance

### Diagnostic Fault Information

Circuit | Short to Ground | Open or High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Fuel Pump High Control | P0231 | P023F | P0232 | P023F, P2635
Fuel Pump Low Control | -- | P023F | -- | P023F, P2635

### Circuit/System Description

The engine control module (ECM) supplies voltage to the fuel pump flow control module (FPCM) when the ECM detects that the ignition is on. The voltage from the ECM to the FPCM remains active for 2 seconds, unless the engine is in crank or run. While this voltage is being received, the FPCM 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 P0191, P0192, P0193, 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 volts.

• | 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 rail pressure and the current estimated fuel rail pressure.

### Action Taken When the DTC Sets

DTC P2635 is a Type A DTC.

### Conditions for Clearing the DTC

DTC P2635 is a Type A 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

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Fuel System Description

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Control Module References

### Circuit/System Testing

1. Verify that DTCs P0192, P0193, P0231, P0232, or P023F are not set.

⇒ | If the DTC is set, refer to DTC P0192 or P0193 or DTC P0231, P0232, or P023F.

2. Ignition OFF, disconnect the harness connector at the fuel tank B47 fuel pump module.
3. Ignition ON, test for less than 5.0 Ω between the fuel pump module low reference circuit terminal 1 and ground.

⇒ | If greater than the specified range, test the fuel pump module low reference circuit for a high resistance. If the circuit tests normal, replace the K27 FPCM.

4. Ignition OFF, install a test lamp between the control circuit terminal 1 and the control circuit terminal 2.
5. Ignition ON, command the fuel pump 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 FPCM.

⇒ | 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 FPCM.

6. Perform the Fuel System Diagnosis

⇒ | If the fuel pressure is not normal, replace the fuel tank B47 fuel pump module.

7. If all circuits test normal, replace the K27 FPCM.

### Repair Instructions

Perform the Diagnostic Repair Verification

• | Fuel Tank Fuel Pump Module Replacement Fuel Pump Module Replacement

• | Control Module References