Ignition On/Off, Basic Function - GF07.10-P-1039A

ENGINE ALL (CAR) 

Overview 

This document contains information on:

• General 
• Function requirements 
• Ignition ON 
• Ignition OFF 

General 

The ignition ON function starts the engine management in the combustion engine control unit and prepares the engine for starting.

The ignition OFF function switches off the engine and subsequently the engine management in the combustion engine control unit.

Function requirements 

• Ignition ON (circuit 15)

Ignition ON 

Upon ignition ON, the electronic ignition lock control unit switches on the circuit 15 relay. Via the conducted on-board electrical system voltage, the engine management in the combustion engine control unit is started. The circuit status is also available to other systems via the vehicle bus systems.

Functions of engine management with ignition ON 

The following functions start if the ignition is switched on and the engine management is started:

• To fully fill the low-pressure fuel circuit and build up pressure, the fuel pump is briefly actuated the first time the ignition is switched on after unlocking the vehicle
• Engine diagnosis indicator lamp is actuated in instrument cluster
• In diesel engines: preglow indicator lamp in instrument cluster and glow output stage are actuated
• Fault memory in combustion engine control unit can be read out and deleted via the diagnostics connection
• Diagnosis or correction programming can be realized via the diagnostics connection
• Throttle valve actuator checks its return spring and performs an actuator adaptation if necessary

Ignition OFF 

Additional function requirements:

• Engine management ON (circuit 87M)

If the ignition is switched off, the electronic ignition lock control unit switches off the circuit 15 relay. The circuit status is also available to other systems via the vehicle bus systems.

Functions of engine management with ignition OFF 

The following components are switched off if the ignition is switched off:

• Fuel pump (FP)
• Fuel injectors
• Quantity control valve
• With spark-ignition engines: ignition coils

The computer run-on of the combustion engine control unit also starts. In this connection, the time until the control unit changes to standby mode is involved.

	Control units
	Combustion engine control unit, basic function		GF07.08-P-9890A