Fuel pump (FP) relay, (2002-2004)
For information about the fuel pump (FP) relay for model year 2005-, see Design and Function .
The following applies for model year 2002-2004
The fuel pump (FP) relay supplies the fuel pump with power. The relay also cuts the power to the pump when the ignition is switched off or if the engine stops. In cars with demand controlled fuel pumps, the above function applies to the fuel pump control module. The central electronic module (CEM) also cuts the power to the relay if the supplemental restraint module (SRS) transmits a message indicating that an airbag has deployed.
The central electronic module (CEM) activates and deactivates the relay when requested by the engine control module (ECM) (via the Controller area network (CAN)).
When the ignition is switched on, the engine control module (ECM) sends a signal to the central electronic module (CEM) via the controller area network (CAN) to run the fuel pump (FP) for one seconds. This is so that the pressure increases in the fuel system, shortening the start time.
When the flywheel in the engine rotates (generating a signal from the engine speed (RPM) sensor), the engine control module (ECM) will transmit a request to the central electronic module (ECM) via the controller area network (CAN) to start the fuel pump. In the event of the engine stopping, the Engine Control Module (ECM) cancels the "activated fuel pump" signal. The central electronic module (CEM) then switches off the fuel pump.
There is a directly connected cable between the engine control module (ECM) and the central electronic module (CEM). In the event of a fault in the controller area network (CAN), this cable is used for the "activated fuel pump" signal.