Fuel Pump Relay

Fuel Pump Relay

the ECM controls operation of the fuel pump via the fuel pump relay in the rear fuse box. the ECM switches the relay coil to earth to energize the relay when the ignition is first turned to position II. the relay remains energized during engine cranking and while the engine is running, but will be de-energized after approximately 2 seconds if the ignition switch remains in position II without the engine running.

A fuel cut-off function is incorporated into the ECM to de-energize the fuel pump in a collision. the cut off function is activated by a signal from the SRS DCU in the event of an airbag activation. the ECM receives an airbag activation signal from the SRS DCU on the CAN Bus.

the fuel cut-off function can only be reset by using TestBook/T4.

the ECM monitors the state of the wiring to the coil winding within the fuel pump relay. the ECM will store relevant fault codes if the ECM detects a problem. the ECM is not able to assess the state of the fuel pump circuit because it is isolated by the function of the relay. However, if the fuel pump circuit fails or the pump fails to deliver sufficient fuel (while the fuel level is above the minimum level), the ECM will store adaptive faults as it tries to increase the air-fuel ratio by increasing the pulse width of the injectors.

Failure of the fuel pump relay will result in the engine failing to start. If the fuel pump fails while the engine is running, the symptoms will be engine hesitation and engine misfire. These symptoms will worsen progressively until the engine stops. the ECM will store several fault codes under this condition.