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

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Special Tools Required

J 43244 Relay Puller Pliers

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 with each command.

1. With the ignition OFF, remove the fuel pump relay from the underhood bussed electrical center.
2. With the ignition ON, engine OFF, probe the control circuit of the fuel pump relay with a test lamp that is connected to a good ground. Command the fuel pump relay ON and OFF with a scan tool.

⇒	If the test lamp does not turn ON and OFF, test for an open, high resistance, or a short to ground in the fuel pump relay control circuit or an intermittent or a poor connection at the ECM. If the circuit tests normal, replace the control module.

⇒	If the test lamp remains illuminated with each command, test for a short to voltage in the control circuit of the fuel pump relay, an intermittent or a poor connection at the ECM. If the circuit tests normal, replace the control module.

3. Connect a test lamp between the control circuit of the fuel pump relay and the ground circuit of the fuel pump relay. Command the fuel pump relay ON and OFF with a scan tool. The test lamp should turn ON and OFF with each command.

⇒	If the test lamp does not turn ON and OFF, repair the open or the high resistance in the ground circuit of the fuel pump relay.

⇒	If the test lamp does turn ON and OFF, test for an intermittent and for a poor connection at the fuel pump relay. If the circuit tests normal, replace the fuel pump relay.

4. Inspect the fuel pump fuse.

⇒	If the fuel pump fuse is open, test for a short to ground in the supply voltage circuit of the fuel pump. If the circuit tests normal, replace the fuel pump.

5. With the ignition ON and engine OFF, probe the ignition positive voltage circuit of the fuel pump relay with a test lamp that is connected to a good ground.

⇒	If the test lamp does not illuminate, repair the open in the ignition positive voltage circuit.

6. Connect a 15A fused jumper wire between the ignition positive voltage circuit of the fuel pump relay and the supply voltage circuit of the fuel pump.

⇒	If the fuel pump operates, test for an intermittent or poor connection at the fuel pump relay, or a faulty fuel pump relay.

⇒	If the fuel pump does not operate, test for an open or high resistance in the supply voltage circuit of the fuel pump, an open or high resistance in the ground circuit of the fuel pump, an intermittent or poor connection at the fuel pump module cover, or a faulty fuel pump module.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.