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. |
Diagnostic Fault Information
Circuit | Short to Ground | High Resistance | Open | Short to Voltage |
|---|---|---|---|---|
Fuel Pump Relay Control | P0230³ | ¹ | P0230³ | P0230² |
Fuel Pump Relay Ground | -- | P0230 | P0230 | ³ |
Fuel Pump Relay Battery Voltage | ³ | ¹ | ³ | ² |
Fuel Pump Supply Voltage | ³ | ¹ | ³ | ² |
Fuel Pump Ground | -- | ¹ | ³ | ³ |
¹ Low current, fuel pump runs slow ² Pump operates continuously, then discharges battery ³ Pump inoperative | ||||
Circuit/System Description
An electric fuel pump is used to prime the fuel system after changing the fuel filter or servicing the fuel system. The fuel pump is part of the diesel fuel conditioning module (DFCM) assembly. The fuel pump is powered by the fuel pump relay. The fuel pump relay is controlled by the engine control module (ECM). The ECM enables the fuel pump when the ignition is turned ON, and will continue to run for two minutes, or until the engine starts. If the engine does not start due to low fuel pressure, and the ignition is left in the ON position, the pump will run for up to two minutes or until the ignition is turned OFF. The ECM will also turn OFF the fuel pump if incorrect voltage is detected on the control circuit. The ECM will need to be powered down with a key cycle during diagnosis or after repairs, before it will command the fuel pump ON again.
Diagnostic Aids
The following conditions may cause the fuel pump fuse to open:
| • | A faulty fuse |
| • | An intermittent short to ground in the supply voltage circuit of the fuel pump |
| • | The fuel pump has an intermittent internal condition |
Reference Information
Schematic Reference
Connector End View Reference
Electrical Information Reference
Scan Tool Reference
Special Tools Required
CH-48027 Digital Pressure Gage
Circuit/System Verification
Install the CH-48027 to the fuel system service port on the right front side of the engine. Command the fuel pump ON with a scan tool and observe the fuel pressure gage. You should either hear or feel the relay click and the fuel pump should turn ON and OFF with each command. Fuel pressure should be a minimum of 69 kPa (10 psi) with the fuel pump running.
Circuit/System Testing
- Inspect the fuel pump fuse.
- Turn ON the ignition, with the engine OFF.
- Command the fuel pump ON and OFF with a scan tool. The fuel pump relay should click and turn ON and OFF with each command.
- Probe the battery positive voltage circuit of the fuel pump relay with a test lamp that is connected to a good ground.
- Connect a fused jumper wire between the battery positive voltage circuit and the supply voltage circuit of the fuel pump relay.
| ⇒ | If the fuel pump fuse is open, test the battery positive voltage circuit and the fuel pump supply voltage circuit for a short to ground or a faulty fuel pump. |
| ⇒ | If the fuel pump operates continuously, test for a faulty relay or a short to voltage in the fuel pump supply voltage circuit. |
| ⇒ | If the fuel pump does not turn ON and OFF, replace the fuel pump relay. |
| ⇒ | If the test lamp does not illuminate, repair the open in the battery positive voltage circuit. |
| ⇒ | If the fuel pump operates, test for an intermittent and for a poor connection at the fuel pump relay, or a faulty fuel pump relay. |
| ⇒ | If the fuel pump does not operate, test for an open or high resistance in the supply voltage circuit, or ground circuit of the fuel pump. |
| ⇒ | If all circuits test normal and the fuel pump relay operates properly, replace the DFCM housing containing the fuel pump. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
