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 that is pulled up to 2.5 volts 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.

P0627

The ECM detects the voltage on the fuel pump relay control circuit is within a predetermined range when the control circuit is commanded OFF. The condition exists for greater than 4 seconds, or for a cumulative time of 30 seconds.

P0628

The ECM detects the fuel pump relay control circuit voltage is less than 2.21 volts when the control circuit is commanded OFF. The condition exists for greater than 4 seconds, or for a cumulative time of 30 seconds.

P0629

The ECM detects the fuel pump relay control circuit voltage is greater than 2.74 volts when the control circuit is commanded ON. The condition exists for greater than 4 seconds, or for a cumulative time of 30 seconds.

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Ignition ON, command the fuel pump relay ON and OFF with a scan tool. You should hear or feel a click from the fuel pump relay.
2. Attempt to start the engine. Observe the DTC information with a scan tool. DTC P0627, P0628, or P0629 should not set.
3. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

1. Ignition OFF, disconnect the fuel pump relay.
2. Connect a test lamp between the control circuit terminal 86 of the fuel pump relay and ground.
3. Ignition ON, command the fuel pump ON and OFF with a scan tool. The test lamp should turn ON and OFF as commanded.

⇒	If the test lamp remains OFF all the time, test the control circuit for a short to ground or an open/high resistance. If circuit/connections test normal, replace the ECM.

⇒	If the test lamp remains ON all the time, test the control circuit for a short to voltage. If circuit/connections test normal, replace the ECM.

4. Ignition OFF, connect a test lamp between the fuel pump relay control circuit terminal 86 and the ground circuit terminal 85 of the fuel pump relay.
5. Ignition ON, command the fuel pump ON and OFF with a scan tool. The test lamp should turn ON and OFF as commanded.

⇒	If the test lamp does not turn ON when commanded, repair the open/high resistance in ground circuit of the fuel pump relay.

6. Ignition ON, test for 2-3 V on the control circuit terminal 86 of the fuel pump relay.

⇒	If not within the specified range, replace the ECM.

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

1. Test for 135-185 Ω between terminals 85 and 86 of the fuel pump relay.

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

2. Measure the resistance between the terminals of the fuel pump relay listed below. The DMM should display O.L.

•

30 and 86

•

30 and 87

•

30 and 85

•

85 and 87

⇒	If less than the specified value, replace the fuel pump relay.

3. Connect a 15 A fused jumper wire from the positive terminal of the battery to relay terminal 86. Connect a jumper wire from the negative terminal of the battery to relay terminal 85. Test for less than 2 Ω between terminals 87 and 30 of the relay.

⇒	If greater than the specified range, replace the fuel pump relay.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.