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 P0627: Fuel Pump Relay Control CircuitDTC P0628: Fuel Pump Relay Control Circuit Low Voltage
DTC P0629: Fuel Pump Relay Control Circuit High Voltage
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Battery Voltage - Relay Switch Side | ¹ | ² | -- | -- |
Fuel Pump Supply Voltage | ¹ | ² | ³ | -- |
Fuel Pump Relay Control | P0628 | P0627 | P0629 | -- |
Fuel Pump Relay Ground | -- | P0627 | -- | -- |
Fuel Pump Ground | -- | ² | -- | -- |
¹ Open fuel pump fuse, cranks, no start ² Cranks, no start ³ Fuel pump operates continuously, discharges battery | ||||
Circuit/System Description
The engine control module (ECM) provides ignition voltage to the coil side of the fuel pump relay whenever the engine is cranking or running. The control module enables the fuel pump relay as long as the engine is cranking or running, and ignition system reference pulses are received. If no ignition system reference pulses are received, the control module turns OFF the fuel pump. The fuel pump relay control circuit is equipped with a feedback circuit within the ECM. The ECM can determine if the control circuit is open, shorted to ground, or shorted to a voltage by monitoring the feedback voltage.
Conditions for Running the DTC
P0627 and P0629
| • | The ignition is ON, with the engine OFF. |
| • | The ignition voltage is greater than 10.5 volts. |
| • | The ECM has commanded the fuel pump relay ON and OFF at least once during the ignition cycle. |
| • | The above conditions are met for more than 1 second. |
| • | The DTCs runs continuously once the above conditions are met. |
P0628
| • | The ignition voltage is greater than 10.5 volts. |
| • | The ECM has commanded the fuel pump relay ON and OFF at least once during the ignition cycle. |
| • | The above conditions are met for more than 1 second. |
| • | The DTCs runs continuously once the above conditions are met. |
Conditions for Setting the DTC
P0627
The ECM detects the fuel pump relay control circuit is open.
P0628
The ECM detects the fuel pump relay control circuit is shorted to ground.
P0629
The ECM detects the fuel pump relay control circuit control circuit is shorted to voltage.
Action Taken When the DTC Sets
DTCs P0627, P0628, and P0629 are Type B DTCs.
Conditions for Clearing the DTC
DTCs P0627, P0628, and P0629 are Type B DTCs.
Reference Information
Schematic Reference
Connector End View Reference
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Special Tools Required
J 43244 Relay Puller Pliers
Circuit/System Verification
Ignition ON, command the fuel pump relay ON and OFF with a scan tool. Listen/feel for relay to click and for fuel pump to turn ON and OFF.
Circuit/System Testing
- Ignition OFF, disconnect the fuel pump relay.
- Ignition ON, connect a test lamp between the relay control circuit terminal and ground.
- Command the relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
- Connect a 15A fused jumper wire between the positive voltage terminal at the battery and the fuel pump voltage supply circuit terminal and verify fuel pump activation.
- Ignition ON, connect a 15A fused jumper wire between the relay switch voltage supply circuit terminal and the fuel pump voltage supply circuit terminal and verify fuel pump activation.
- Ignition ON, verify that a test lamp illuminates between the relay coil ground circuit terminal and B+.
- If all circuits and the ECM test normal, test or replace the fuel pump relay.
| ⇒ | If the test lamp is always ON, test the relay control circuit for a short to voltage. If the circuit tests normal, replace the ECM. |
| ⇒ | If the test lamp is always OFF, test the relay control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM. |
| ⇒ | If the fuel pump does not activate, test the fuel pump voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the fuel pump. |
| ⇒ | If the fuel pump does not activate, test the relay switch voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal and it's fuse is open, test or replace the relay. |
| ⇒ | If the test lamp does not illuminate, test the relay coil ground circuit for an open/high resistance. |
Component Testing
Relay Test
- Ignition OFF, disconnect the fuel pump relay.
- Test for 70-110 ohms of resistance between terminals 85 and 86.
- Test for infinite resistance between the following terminals:
- Test for less than 2 ohms of resistance between terminals 30 and 87A.
- Install a 15A fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms of resistance between terminals 30 and 87.
| ⇒ | If the resistance is not within the specified range, replace the relay. |
| • | 30 and 86 |
| • | 30 and 87 |
| • | 30 and 85 |
| • | 85 and 87 |
| ⇒ | If not the specified value, replace the relay. |
| ⇒ | If greater than the specified range, replace the relay. |
| ⇒ | If greater than the specified range, replace the relay. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for ECM replacement, setup, and programming |
