BODY CONTROL UNIT: DESCRIPTION AND OPERATION (page 3 of 16)

BODY CONTROL UNIT

DESCRIPTION AND OPERATION 86-3-21

Security system status LED
The LED flashes when the anti-theft system has been set. There are four different flash rates dependent on mode of 
operation or other system information.

Central door locking
The doors can be locked by the following methods:

l

Pressing the lock button on the remote transmitter.

l

Locking the vehicle from the driver's door with the key.

l

Pressing the lower half of the central door lock switch.

l

Pushing the sill button down (will only lock that particular door).

l

By driving over 7 km/h (4 mph) – ( if the speed related locking function has been enabled).

The BCU will prevent locking if the logical conditions for locking are not satisfied. Conditions which will prevent door 
locking include:

l

Driver's door open.

l

Ignition switch on.

l

Inertia switch tripped.

l

Vehicle is already superlocked.

A mislock may occur if the logical conditions are not met.

The doors can be unlocked by the following methods:

l

Pressing the unlock button on the remote transmitter

l

Unlocking the vehicle from the driver's door with the key.

l

Pressing the upper half of the central door locking switch (not operational if the vehicle is superlocked).

l

Pulling the interior door handles (not operational if the vehicle is superlocked).

l

Inertia switch being triggered while the ignition is on and the security system is de-activated.

The BCU supplies information via the serial data bus to the IDM to energise the coil of the relays for each of the door 
lock actuators.

The BCU normally checks the following inputs to determine lock/ unlock requirements:

l

Unlock request.

l

Lock request.

l

Superlock request.

l

Single point entry request.

l

Lock passenger and rear doors request.

The following outputs are generated by the BCU dependent on the prevailing logic conditions and the input requests 
the BCU has detected:

l

Unlock all doors enable.

l

Lock passenger and rear doors enable.

l

Superlock all doors enable.

l

Lock driver's door enable.

All lock/ unlock pulses have a duration of 800 ms.

Input/Output logic for door lock/unlock

To determine if the vehicle speed is appropriate for enabling speed related locking, the BCU uses the vehicle speed 
signal supplied over the serial data bus from the instrument pack.

Output/Request

Superlock all 
doors enable

Unlock all doors 

enable

Lock driver's 

door enable

Lock passenger 

and rear doors 

enable

Unlock request

0

1

0

0

Lock request

0

0

1

1

Superlock request

1

0

1

1

Single point entry request

0

1

0

1

Lock passenger and rear doors request

0

0

0

1