Operation

OPERATION

General

Feed from the positive battery terminal (C0192) is supplied to the main relay and fusible link 3 (C0632) on an R wire. Both are located in the engine compartment fuse box.

The battery also provides a feed to fusible link 4 of the engine compartment fuse box (C0632) on vehicles fitted with an instrument dimmer switch. For more information, refer to the Interior Lamps section of this manual.  INTERIOR LAMPS.

Operation of the main relay (C0576 on Td4 vehicles, C0578 on KV6 vehicles) is controlled by the Engine Control Module (ECM) (C0603 on Td4 vehicles, C0604 on KV6 NAS vehicles, C0371 on KV6 ROW vehicles) on a WK wire (NG on KV6 NAS vehicles). The energised main relay allows a battery feed to flow to fuse 4 of the engine compartment fuse box. Fuse 4 (C0575) provides a feed to the following on NK wires:

The Automatic Transmission Control Unit (ATCU) (C0932). The transmission selector (C0244) (vehicles without instrument dimmer only). The illumination relay (C1976) (vehicles with instrument dimmer only). The Steptronic switches (C0410).

For further details of main relay operation, refer to the Engine Management – EDC , Engine Management – Siemens (NAS) or Engine Management – Siemens (All Except NAS) section of the System Description and Operation Workshop manual.

Fusible link 3 (C0571) is connected to the ignition switch (C0028) by an N wire. When the ignition switch is turned to the 'ignition' position, current flows across the switch (C0028) to fuse 35 of the passenger compartment fuse box (C0588) on a G wire. Fuse 35 (C0580) provides an ignition feed to the transmission inhibit switch (C0244) on a W wire.