Body control unit (Operation): Description and operation

Operation

For IDM inputs which are also inputs for BCU functions, the delay before the BCU recognises the change in input status is less than 250 ms. The BCU uses a debounce algorithm to ignore changes in input having a duration less than 100 ms with the exception of automatic gearbox W, X, Y, Z inputs, which have a debounce period of 33 ms.

Transit mode

To prevent excessive battery drain during transit to overseas markets, the vehicle is placed in a transit mode.

To exit the transit mode, simultaneously hold down the heated rear window switch and the rear fog lamp switch, turn the ignition switch from 0 to II and, after a minimum of 2 seconds, release the switches.

Transit mode can be entered using TestBook. When TestBook communicates with the BCU for diagnostics related to BCU operation, it first checks that the vehicle is not in transit mode.

Anti-theft system

The BCU uses the driver's door key lock and unlock switches to activate and deactivate the security system. The driver's door lock is also used for entering the EKA. ALARM SYSTEM AND HORN, DESCRIPTION AND OPERATION, Description.

Immobilisation For immobilisation, the BCU disables the starter motor relay. When the engine is cranking, the ECM looks for a coded signal from the BCU. If the signal is not received within one second of cranking, the fuel supply to the engine is stopped and the injectors are disabled. This also prevents unburnt fuel from entering the catalyst.

If the BCU is disconnected, the engine starter motor will remain isolated by the starter motor relay and the ECM will remain immobilised. The main wiring for the system is contained within the main harness which is relatively inaccessible, so preventing intruders from disabling the system by cutting the wires for the immobilisation system. Once the immobiliser has been activated, destruction of the trigger device or the wiring to it will not disarm the system.

The RF transmitter communicates to the BCU via the RF receiver using a 70 bit code. Pressing the unlock button on the transmitter will re-mobilise the vehicle. The RF transponder is integrated into the metal key assembly, inserting the key into the ignition switch will induce a signal in the exciter coil to re-mobilise the vehicle.

Anti-theft alarm The alarm system provides a warning of unauthorised access to the vehicle and includes perimetric and volumetric monitoring under the control of the BCU.

The perimetric protection system detects opening of all doors, tail door and bonnet and will also detect the operation of the ignition key switch. The following conditions must be satisfied before the BCU will operate all of the functions of perimetric protection: l All doors and hinged panels are in the closed position. l Ignition key out of the ignition switch. l Inertia switch is not tripped.

If all conditions are not satisfied the BCU will enter a mislock condition.

The volumetric sensor uses two ultrasonic sensors mounted in the headlining to detect movement within the vehicle. The alarm will trigger when the sensor signals the BCU for 200 ms or greater. Within a single setting period the alarm system will allow a maximum of 10 triggers as a result of any combination of sensor inputs. It is possible to lock the vehicle without enabling the volumetric alarm by using the key. The same conditions needed to satisfy enabling of the perimetric protection system is also needed to enable volumetric protection.