For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### DTC Descriptors

DTC P0231: Fuel Pump Control Circuit Low Voltage
DTC P0232: Fuel Pump Control Circuit High Voltage
DTC P023F: Fuel Pump Control Circuit

### Diagnostic Fault Information

Circuit | Short to Ground | Open or High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Fuel Pump High Signal | P0231 | P023F | P0232 | P023F, P2635
Fuel Pump Low Signal | -- | 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 two seconds, unless the engine is in crank or run. While this voltage is being received, the FPCM supplies a varying voltage to the fuel tank pump module in order to maintain the desired fuel rail pressure.

### Conditions for Running the DTC

#### P0231, P023F

The ignition voltage is between 9-18 volts

#### P0232

The control enable voltage signal supplied for the ECM to FPCM is inactive for 4 seconds after engine has been shut off.

### Conditions for Setting the DTC

The FPCM detects a fault on the fuel pump voltage circuit that is above or below a predetermined voltage threshold.

### Action Taken When the DTC Sets

DTCs P0231, P0232, and P023F are Type A DTCs.

### Conditions for Clearing the DTC

DTCs P0231, P0232, and P023F are Type A DTCs.

### 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 for scan tool information

### Circuit/System Verification

Ignition ON, command the fuel pump ON and OFF using the scan tool ECM fuel pump output control. The fuel pump should turn ON and OFF.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the fuel pump.
2. Connect a test lamp between the control circuit terminal 1 and ground.
3. Ignition ON, command the fuel pump ON and OFF using a scan tool ECM fuel pump output control. The test lamp should turn ON and OFF as commanded.

⇒ | If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the 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 FPCM.

4. Ignition OFF, connect a test lamp between the control circuit terminal 2 and the control circuit terminal 1.
5. Ignition ON, command the fuel pump ON using a scan tool. The test lamp should illuminate.

⇒ | If the test lamp does not illuminate, test the control circuit terminal 2 for a short to voltage or an open/high resistance. If the circuit tests normal, replace the FPCM.

6. If all circuits test normal, replace the fuel tank fuel pump module.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Fuel Tank Module Replacement

• | Control Module References for FPCM replacement, setup, and programming