The secondary fuel pump is located in the rear fuel tank. The secondary fuel pump is powered by a secondary fuel pump relay. Fuel is transferred from the rear fuel tank to the front fuel tank in order to ensure all of the usable fuel volume is available to the primary fuel pump. The secondary fuel pump relay is controlled by the engine control module (ECM). If the engine is running the secondary fuel pump is normally ON.

The ECM does not detect a change of 3 L (0.7925 gal), in both the primary and the secondary fuel level sensors, with the secondary pump commanded ON for 200 seconds.

DTC P2636 is a Type B DTC.

DTC P2636 is a Type B DTC.

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

Special Tools

J 43244 Relay Puller Pliers

Important: An open or a short to voltage in the control circuit will cause both the Ckt. Open Test Status and the Ckt. Short Volts Test Status parameters to display Fault.

Ignition ON, command the fuel pump relay ON and OFF with a scan tool while observing the following control circuit status parameters:

Each parameter should toggle between OK and Not Run or Not Run and OK.

1. Ignition OFF, disconnect the fuel pump relay.
2. Ignition ON, verify that a test lamp illuminates between the ground circuit terminal 85 and B+.

⇒	If the test lamp does not illuminate, test the ground circuit for a short to voltage or an open/high resistance.

3. Verify that a test lamp does not illuminate between the ground circuit terminal 85 and the control circuit terminal 86.

⇒	If the test lamp illuminates, test the control circuit for a short to voltage. If the circuit tests normal, replace the ECM.

4. Remove the test lamp.
5. Command the fuel pump relay ON with a scan tool. Verify the scan tool fuel pump relay Ckt. Short Grnd Test Status parameter is OK.

⇒	If not the specified value, test the fuel pump relay control circuit for a short to ground. If the circuit tests normal, replace the ECM.

6. Install a 3A fused jumper wire between the fuel pump relay control circuit terminal 86 and the ground circuit terminal 85. Command the fuel pump ON with a scan tool. Verify the scan tool fuel pump relay Ckt. Short Grnd Test Status parameter is Fault.

⇒	If not the specified value, test the fuel pump relay control circuit for an open/high resistance. If the circuit tests normal, replace the ECM.

7. Inspect the fuel pump fuse.

⇒	If the fuel pump fuse is open, test for the following conditions:

•	A short to ground in the relay switch B+ circuit

•	A short to ground in the supply voltage circuit of the fuel pump

⇒	If the above circuits test normal, replace the fuel tank module.

8. Verify that a test light illuminates between the B+ circuit and ground.

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

9. Connect a 15A fused jumper wire between the B+ circuit and the supply voltage circuit of the fuel pump. Verify the fuel pump is activated.

⇒	If the fuel pump does not activate, test for the following conditions:

•	An open/high resistance in the supply voltage circuit of the fuel pump

•	An open/high resistance in the ground circuit of the fuel pump

⇒	If the above circuits test normal, replace the fuel tank module.

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.