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

BODY CONTROL UNIT

86-3-34 DESCRIPTION AND OPERATION

Key-in warning
The BCU can be programmed to one of two options:

l

Option 1 – no timeout.

l

Option 2 – no key-in warning.

The BCU issues an audible warning No. 2 request, depending on the status of the following inputs:

l

Ignition state.

l

Ignition key inserted.

l

Driver's door open.

If the key-in warning is programmed into the BCU for operation, audible warning No.2 will be requested if the ignition 
switch is off, the ignition key inserted signal is on and the driver's door open signal is ON.

In the event of a communications link failure occurring, the audible warning request is not sent to the instrument pack.

SLABS HDC warning
The BCU issues an audible warning No. 3 request, depending on the status of the following inputs:

l

Ignition state.

l

SLABS HDC warning.

The SLABS warning transmitted by the SLABS ECU is a 2 Hz signal, audible warning No. 3 is requested on every 
falling edge of this signal. If the signal from the SLABS ECU stays low for more than 650 ms, audible warning No. 3 
is requested every 2 seconds, for 30 seconds, while the signal stays low.

In the event of a communications link failure occurring, the audible warning request is not sent to the instrument pack.

Transfer box in neutral warning
If the transfer box is in the neutral position and the ignition switch is on, the BCU issues an audible warning No. 4 
request. The BCU checks for the following inputs:

l

Transfer box neutral selected.

l

Ignition on.

The transfer box in neutral warning is activated by communicating with the instrument pack via the serial datalink. If 
a communications link failure occurs while the transfer box in neutral warning is active, the audible warning will not 
operate.

Lights on warning
If the ignition switch is off while the side lamps or headlamps on and the driver's door is opened, the BCU issues an 
audible warning No. 5 request.

The BCU checks for the following inputs:

l

Driver's door open.

l

Ignition on.

l

Side lamps.

l

Dipped beam state.

l

Main beam state.

The lights on warning is activated by communicating with the instrument pack via the serial datalink. If a 
communications link failure occurs while the lights on warning is active, the audible warning will not operate.

SLABS raise/lower
Before enabling a SLS vehicle raise/ lower request, the BCU checks the logical condition of the following inputs:

l

Ignition state.

l

SLABS raise request.

l

SLABS lower request.

If the ignition switch is in position 0 or I, the vehicle raise/ lower request is off.

With the ignition switch in position II, and the 'SLABS raise' request and 'SLABS lower' request both off, the vehicle 
raise/ lower request output is driven at 25 Hz with a 50% duty cycle and the vehicle height remains unchanged. 

If the 'SLABS lower' request input is on, the vehicle raise/lower request output is driven at 25 Hz with a 25% duty cycle, 
lowering the vehicle. 

If the 'SLABS raise' request input is on, the vehicle raise/lower request output is driven at a 25 Hz with a 75% duty 
cycle.