Engine Management System Operation

Engine Starting
When the ignition switch is in position II a power feed is connected from the ignition switch to the ECM relay and the ECM. The ECM then initiates 'wake up' routines and energizes the main and fuel pump relays.

When the engine cranks, provided a valid mobilization signal is received from the immobilization ECU, the ECM initiates throttle control, fuelling and ignition to start and maintain control of the engine as necessary to meet driver demand. If no mobilization code is received from the immobilization ECU, or the code is invalid, the ECM inhibits fuel injection and ignition to prevent the engine from starting.

The electrical circuit from the fuel pump relay to the fuel pump is routed through the fuel cut-off inertia switch, located below the E-box in the engine compartment. In the event of a collision the switch breaks the circuit to prevent further fuel being delivered to the engine. The switch is reset by pressing down the center of the rubber cover on the top of the switch.

During the start sequence, the ECM also illuminates the MIL, as a bulb check. While the ignition switch is in position II the MIL is continuously illuminated. The MIL is extinguished when the ignition switch turns to position III and the engine starts.

Engine Stopping
When the ignition switch is turned to position I, the ECM switches off the ignition coils and fuel pump to stop the engine and the ECM relay de-energizes to disconnect the power feed to the fuel injectors. The ECM continues to energize the main relay until the power down functions are completed. Power down functions include the fuel tank leak check, engine cooling and memorising data for the next start up. If neither a fuel tank lank check nor engine cooling are required, the power down process takes approximately 10 seconds.

When the power down process is completed, the ECM de-energizes the main relay and enters a low power mode. In the low power mode, maximum quiescent drain is 0.5 mA.