P2636

DTC P2636

CIRCUIT DESCRIPTION
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 supply voltage is received from the primary fuel pump relay when the primary fuel pump is energized. This DTC sets when the powertrain control module (PCM) commands the secondary fuel pump ON and a predetermined change in both the front and rear fuel level sensors does not occur.

DTC DESCRIPTOR
This diagnostic procedure supports the following DTC:
DTC P2636 Fuel Transfer Pump Flow Insufficient

CONDITIONS FOR RUNNING THE DTC
- DTCs P0461, P0462, P0463, P2066, P2067, P2068 are not set.
- The vehicle speed is 0 km/h (0 mph).
- The engine has been idling for more than 2 minutes and 20 seconds.
- The primary fuel level is less than 60 L (15.8 gal).
- The secondary fuel level is more than 3 L (2.6 gal).

CONDITIONS FOR SETTING THE DTC
The PCM does not detect a change of 4 L (1.06 gal), in both the primary and the secondary fuel level sensors, with the secondary pump commanded ON for 120 seconds.

ACTION TAKEN WHEN THE DTC SETS
- The PCM stores the DTC information into memory when the diagnostic runs and fails.
- The malfunction indicator lamp (MIL) will not illuminate.
- The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Failure Records.
- The driver information center, if equipped, may display a message.

CONDITIONS FOR CLEARING THE DTC
- A current DTC Last Test Failed clears when the diagnostic runs and passes.
- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
- Clear the DTC with a scan tool.

TEST DESCRIPTION

Steps 1-8:

Steps 9-18:

Steps 19-31:

Step 32:

The numbers below refer to the step numbers on the diagnostic table.
2. This step tests the supply voltage circuit of the secondary fuel pump relay. The test lamp should illuminate as the primary fuel pump is commanded ON.
4. This step verifies the secondary fuel pump operation. Listen for an audible sound as the secondary fuel pump relay harness connector is jumpered.
5. This step verifies that there is adequate fuel in the rear fuel tank. The rear fuel tank sensor voltage must be above 1 volt in order to continue.
7. This step tests the secondary fuel pumps ability to transfer fuel. The rear fuel level sensor voltage should decrease while the secondary fuel pump is ON.
8. This step tests for a short to ground on the control circuit of the secondary fuel pump relay. If the test lamp illuminates, a short to ground is indicated.
9. This step tests for a short to voltage on the control circuit of the secondary fuel pump relay. If the test lamp illuminates, a short to voltage is indicated.
10. This step verifies the secondary fuel pump relay operation. An audible click should be heard as the secondary fuel pump relay control circuit is grounded. The secondary fuel pump should turn ON as the fuel pump relay control circuit is grounded.