P0627-FUEL PUMP CONTROL CIRCUIT

For a complete wiring diagram Refer to Section 8W.

When Monitored:
With the ignition on. Battery voltage greater than 10.4 volts and the ASD sense switch is on.
Set Condition:
Actual Fuel Pump Relay state is not equal to desired state. One Trip Fault. Three good trips to turn off the MIL.

Possible Causes

(F1) FUSED IGNITION SWITCH OUTPUT CIRCUIT

INTERNAL FUSED B+ CIRCUIT

(K31) FUEL PUMP RELAY CONTROL CIRCUIT

(K31) FUEL PUMP RELAY CONTROL CIRCUIT SHORTED TO GROUND

FUEL PUMP RELAY

PCM

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).

Diagnostic Test

1. FUEL PUMP RELAY OPERATION

Ignition on, engine not running.
With a scan tool, actuate the Fuel Pump Relay.

Is the Fuel Pump Relay operating?

Yes

Refer to the INTERMITTENT CONDITION Diagnostic Procedure.

Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Go To 2

2. FUEL PUMP RELAY

Turn the ignition off.
Remove the Fuel Pump Relay from the PDC.
Measure the resistance of the Fuel Pump Relay Coil.

Is the resistance between 70 to 90 ohms?

Yes

Go To 3

Replace the Fuel Pump Relay.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

3. FUSED B+ CIRCUIT

Using a 12-volt test light connected to ground, probe the Fused B+ circuit.

Does the test light illuminate brightly?

Yes

Go To 4

Repair the open or short to ground in the Fused B+ circuit. Inspect the related fuse and repair as necessary.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

4. (F1) FUSED IGNITION SWITCH OUTPUT CIRCUIT

Ignition on, engine not running.
Using a 12-volt test light connected to ground, probe the (F1) Fused Ignition Switch Output circuit.

Does the test light illuminate brightly?

Yes

Go To 5

Repair the open or short to ground in the (F1) Fused Ignition Switch Output circuit. Inspect the related fuse and repair as necessary.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

5. (K31) FUEL PUMP CONTROL CIRCUIT OPEN

Turn the ignition off.
Disconnect the C3 PCM harness connector.

CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #8815 to perform diagnosis.

Measure the resistance of the (K31) Fuel Pump Relay Control circuit from the PDC to the appropriate terminal of special tool #8815.

Is the resistance below 5.0 ohms?

Yes

Go To 6

Repair the open in the (K31) Fuel Pump Relay Control circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

6. (K31) FUEL PUMP CONTROL CIRCUIT SHORTED TO GROUND

Measure the resistance between ground and the (K31) Fuel Pump Relay Control circuit in the PDC.

Is the resistance below 100 ohms?

Yes

Repair the short to ground in the (K31) Fuel Pump Relay Control circuit.

Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Go To 7

7. PCM

NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.

Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.

Were there any problems found?

Yes

Repair as necessary.

Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Replace and program the Powertrain Control Module per Service Information.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)