The engine control module (ECM) provides a ground to the coil side of the fuel pump relay. When the ignition switch is first turned ON, the ECM energizes the fuel pump relay, which applies power to the fuel pump. The ECM enables the fuel pump relay as long as the engine is cranking or running, and crankshaft reference pulses are received. If no crankshaft reference pulses are received, the ECM de-energizes the fuel pump relay after about 3 seconds.

P0628

The ECM detects the fuel pump relay control circuit is open or shorted to ground.

P0629

The ECM detects the fuel pump relay control circuit is shorted to voltage.

DTC P0628 and P0629 are Type C DTCs.

DTC P0628 and P0629 are Type C DTCs.

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

1. With the ignition ON, command the fuel pump relay ON with a scan tool. You should hear an audible click for about 3-5 seconds.
2. If the vehicle passes the Circuit/System Verification Test, then operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records Data List.

1. Ignition OFF, disconnect the harness connector of the fuel pump relay.
2. Ignition ON, verify that a test lamp illuminates between the ignition 1 voltage circuit and battery ground.

⇒	If the test lamp does not illuminate, test the ignition 1 voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition 1 voltage circuit fuse is open, test all components connected to the ignition 1 voltage circuit and replace as necessary.

3. Connect a test lamp between the control circuit and the ignition 1 voltage circuit.
4. Command the fuel pump relay ON with a scan tool. The test lamp should pulse ON and OFF for 3-5 seconds.

⇒	If the test lamp is always ON, test the control circuit for a short to ground. If circuit/connections test normal, replace the ECM.

⇒	If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If circuit/connections test normal, replace the ECM.

5. If all circuits/connections test normal, test or replace the fuel pump relay.

1. Measure for 70-110 ohms of resistance between terminals 85 and 86 of the fuel pump relay.

⇒	If the resistance is not within the specified range, replace the fuel pump relay.

2. Measure for infinite resistance between the following terminals of the fuel pump relay:

•

30 and 86

•

30 and 87

•

30 and 85

•

85 and 87

⇒	If continuity is detected, replace the fuel pump relay.

3. Connect a 20-amp fused jumper wire from the positive terminal of the battery to relay terminal 85. Connect a jumper wire from the negative terminal of the battery to relay terminal 86. Measure for less than 2 ohms between terminals 30 and 87 of the relay.

⇒	If the resistance measures more than 2 ohms, replace the fuel pump relay.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.