When you turn ON the ignition switch, the engine control module (ECM) energizes the fuel pump relay which powers the fuel pump ON. The fuel pump remains ON as long as the engine is cranking or running and the ECM receives ignition reference pulses. If there are no ignition reference pulses, the ECM shuts the fuel pump OFF within 2 s after the ignition was switched to the ON position or if the engine stops.

The following conditions may cause the fuel pump fuse to open:

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Fuel System Description

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

Special Tools

EL-43244 Relay Puller Pliers

For equivalent regional tools, refer to LINK 177833.

With the ignition ON, engine OFF, command the fuel pump relay ON and OFF several times using the scan tool output control function. You should either hear or feel the relay click and the fuel pump should turn ON and OFF with each command.

1. Ignition OFF, the G12 Fuel Pump should not be running.

⇒	If the G12 Fuel Pump runs continuously, test the KR23A Fuel Pump Relay switch supply circuit terminal 87 for a short to voltage. If the circuit tests normal, replace the KR23A Fuel Pump Relay.

2. Ignition OFF, remove the KR23A Fuel Pump Relay from the electrical center with the EL-43244 Relay Puller Pliers .
3. Verify a test lamp illuminates between the KR23A Fuel Pump Relay ground circuit terminal 85 and B+.

⇒	If the test lamp does not illuminate, repair the ground circuit for an open / high resistance.

4. Ignition ON, test for 2 to 3 V between the K20 Engine Control Module (ECM) control circuit terminal 86 and ground.

⇒	If less than the specified range, test the K20 Engine Control Module (ECM) control circuit for a short to ground, or an open / high resistance. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

⇒	If greater than the specified range, test the K20 Engine Control Module (ECM) control circuit for a short to voltage. If the circuit / connections test normal, replace the K20 Engine Control Module (ECM).

5. Command the G12 Fuel Pump ON with a scan tool. The DMM should transition from 2 to 3 V when commanded OFF to greater than 10 V when commanded ON.

⇒	If the circuit voltage does not correspond to the specified values, replace the K20 Engine Control Module (ECM).

6. Verify a test lamp illuminates between the KR23A Fuel Pump Relay switch B+ voltage circuit terminal 30 and ground.

⇒	If the test lamp does not illuminate, repair the KR23A Fuel Pump Relay switch B+ voltage circuit for a short to ground or an open / high resistance.

7. Install a 15 A fused jumper wire between the KR23A Fuel Pump Relay switch B+ voltage circuit terminal 30 and the KR23A Fuel Pump Relay switch supply circuit terminal 87. The G12 Fuel Pump should turn ON.

⇒	If the fuel pump does not turn ON, test the KR23A Fuel Pump Relay switch supply circuit and the G12 Fuel Pump motor ground circuit for an open / high resistance. If the circuits test normal, replace the G12 Fuel Pump.

8. If all circuits test normal, test or replace the KR23A Fuel Pump Relay.

Static Test

1. Ignition OFF, remove the KR23A Fuel Pump Relay from the electrical center with the EL-43244 Relay Puller Pliers .
2. Test for 70 to 110 Ω between terminals 85 and 86.

⇒	If not within the specified range, replace the KR23A Fuel Pump Relay

3. Test for infinite resistance between the following terminals:

•

30 and 86

•

30 and 87

•

30 and 85

•

85 and 87

⇒	If not the specified value, replace the KR23A Fuel Pump Relay.

4. Install a 20A fused jumper wire between KR23A Fuel Pump Relay terminal 85 and 12 V. Install a jumper wire between KR23A Fuel Pump Relay terminal 86 and ground. Test for less than 2 Ω between terminals 30 and 87.

⇒	If greater than the specified range, replace the KR23A Fuel Pump Relay.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.