Ignition ON, function

Function requirements for ignition ON, general points

 Terminal 30

Ignition ON, general points

With ignition ON, the engine timing in the CDI control unit (N3/9) is switched on and the engine prepared for starting.

Function sequence for ignition ON

When the ignition is switched on, the electronic ignition lock control unit (N73) forwards the on-board voltage from "circuit 30" to "circuit 15" over the engine compartment circuit 15 relay (K40/8kH).

If a voltage is applied to the CDI control unit at "circuit 15", the engine circuit relay 87M (K40/8kN) is actuated by means of a ground signal.

This causes the relay to close its power contact and, according to the corresponding electrical fuses, the "circuit 30" voltage is passed on as "circuit 87 " to the CDI control unit and to the corresponding sensors and actuators of the engine timing.

If a voltage is present at "circuit 87", the engine timing is switched on and an output stage driver in the CDI control unit takes over further actuation of the circuit relay 87M.

The "circuit 31" ground connection is made from the on-board electrical system battery (G1) via the battery ground point (W10) and multiple ground lines to the front right assembly compartment ground point (for lamp unit) (W2).

When the engine timing is switched on, the CDI control unit carries out the following functions:

– for cylinder flooding protection, the fuel pump (M3) is actuated over the drive train CAN (CAN C1) and over the fuel system control unit (N118) (only the first time the ignition is switched ON after the vehicle is unlocked).

– in the instrument cluster (A1) the engine diagnosis indicator lamp symbol is actuated for checking by the CDI control unit via the engine CAN, the powertrain control unit (N127), the suspension FlexRay, the electronic ignition lock control unit (N73) and the user interface CAN.

– data are exchanged with the electronic ignition lock control unit and the powertrain control unit (circuit 50 signal and drive authorization) over the suspension FlexRay and engine CAN.

– actuation of the glow output stage (N14/3) via drive train LIN (LIN C1). The glow output stage then responds by actuating the glow plugs (R9) on the positive side. The preglow indicator lamp symbol is actuated over the engine CAN, powertrain control unit, suspension FlexRay, electronic ignition lock control unit, user interface CAN and the instrument cluster.

– the fault memory in the CDI control unit can be read out and deleted via the diagnostic connector (X11/4) with Xentry Diagnostics.

– diagnosis is possible with Xentry Diagnostics via diagnostic CAN (CAN D) and via the diagnostic connector.

– the throttle valve actuator (M16/6) checks its return spring (by the position of the throttle valve) and adapts the position of the actuator, if necessary.