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 a cumulative of 50 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 a cumulative of 50 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 a cumulative of 50 seconds.

DTCs P0627 and P0628 are Type C DTCs.

DTC P0629 is a Type B DTC.

DTCs P0627 and P0628 are Type C DTCs.

DTC P0629 is a Type B DTC.

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Description and Operation

Throttle Actuator Control (TAC) System Description

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Ignition ON, command the Fuel Pump Relay ON and OFF with a scan tool. You should hear an audible click.

1. Ignition OFF, disconnect the fuel pump relay.
2. Connect a test lamp between the control circuit 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 the circuit tests normal, replace the ECM.

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

4. Ignition OFF, connect a test lamp between the fuel pump relay control circuit and the ground circuit.
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 the ground circuit.

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

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

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

1. Measure for 110-150 ohms of resistance between terminals 1 and 2 of the fuel pump relay.

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

2. Measure for infinite resistance between the following terminals:

•

3 and 2

•

3 and 5

•

3 and 1

•

1 and 5

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

3. Connect a 15A fused jumper wire from the positive terminal of the battery to relay terminal 1. Connect a jumper wire from the negative terminal of the battery to relay terminal 2. Measure for less than 2 ohms between terminal  3 and 5 of the relay.

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.