P2636

DTC P2636

CIRCUIT DESCRIPTION
The fuel pump is located on the left frame rail between the fuel tanks. The engine control module (ECM) provides ignition positive voltage to the coil side of the fuel pump relay. The ECM energizes the fuel pump relay, which applies power to the fuel transfer pump. 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 engine. If the ECM commands the transfer fuel pump ON and a predetermined change in the front and rear fuel level sensors does not occur, this DTC sets.

DTC DESCRIPTOR
This diagnostic procedure supports the following DTC:
DTC P2636 Fuel Pump 2 Flow Insufficient

CONDITIONS FOR RUNNING THE DTC
- DTC P0500 is not set.
- The engine is running.
- The vehicle speed is 0 km/h (0 mph).
- The primary fuel level is less than 25 liters (6.6 gallons).
- The secondary fuel level is between 3-10 liters (0.8-2.6 gallons).
- The above conditions are met for 20 seconds before the fuel transfer pump is commanded ON.
- The fuel transfer pump is commanded ON for 120 seconds.

CONDITIONS FOR SETTING THE DTC
The ECM detects a primary fuel level increase and a secondary fuel level decrease of less than 2.6 liters (0.70 gallons) each, within 120 seconds.

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

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.

DIAGNOSTIC AIDS
- When outside temperatures are below 0°C (32°F), the fuel tank pickup screen may ice over from water in the fuel tank.
- If the engine is running while fueling the vehicle, this DTC may set.
- The fuel will default to empty when this DTC sets.

TEST DESCRIPTION










The numbers below refer to the step numbers on the diagnostic table.
3. This step determines if the condition is on the coil side or the switch side of the fuel pump relay.
11. This step verifies the fuel transfer pump operation. If the test lamp flashes, the fuel transfer pump and circuits are OK.