Body Control Unit Operation and Description for Land Rover Discovery II
BODY CONTROL UNIT
DESCRIPTION AND OPERATION 86-3-33
In the event of a communications link failure occurring while the transfer box enable is on, the output will be switched
off.
Gear position switch
On automatic gearbox models, the BCU provides an output which supplies power to the automatic gearbox gear
position switch. The BCU checks for the following inputs before it supplies power:
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Ignition on.
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Auxiliary.
When the ignition is on, the feed to the gear position switch is on. When the ignition is off and auxiliary is off for more
than 30 seconds, feed to the gear position switch is off.
AUTOMATIC GEARBOX - ZF4HP22 - 24, DESCRIPTION AND OPERATION, Description.
Fuel flap release
The fuel flap release solenoid only operates when the ignition switch is switched off, the anti-theft system is not
activated and the fuel flap release switch is pressed. If the BCU detects that these conditions have been satisfied, it
provides a path to earth for the fuel flap solenoid, so allowing the fuel flap to be opened.
To decide the correct conditions for providing a fuel flap enable output, the BCU checks the following input conditions:
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Ignition state.
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Perimetric alarm state.
If the battery state is not normal, the electric fuel flap enable is switched off.
Audible warnings
The BCU can request the instrument pack to generate an audible warning in response to logic conditions which have
been detected by the BCU and which need to be drawn to the driver's attention.
INSTRUMENTS, DESCRIPTION AND OPERATION, Description.
Seat belt warning
The BCU can be programmed to include seat belt warning using one of four options:
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Option 1 – warning on for 6 seconds.
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Option 2 – warning on for 6 seconds or until the seat belt is fastened.
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Option 3 – warning on for 6 seconds unless the seat belt is fastened.
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Option 4 – no warning.
The BCU checks the status of the following inputs:
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Ignition on.
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Seat belt fastened.
Depending on the logic conditions of the inputs, the BCU provides the following outputs:
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Audible warning No.1 requested.
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Seat belt not fastened warning on instrument pack (via datalink to the instrument pack).
When programmed for option 1 operation, audible warning No. 1 is requested when the ignition switch is turned from
off to position II. The audible warning remains active for 6 seconds and a warning lamp on the instrument pack is
illuminated for the same duration.
When programmed for option 2 operation, audible warning No. 1 is requested when the ignition switch is turned from
off to position II. The audible warning remains active for 6 seconds or until the seat belt fastened signal is on and a
warning lamp on the instrument pack is illuminated for the same duration.
When programmed for option 3 operation, audible warning No. 1 is requested when the ignition switch is turned from
off to position II. The audible warning remains active for 6 seconds if the seat belt fastened signal is off; a warning
lamp on the instrument pack is illuminated for the same duration.
In the event of a communications link failure occurring, the audible and visual warning requests are not sent to the
instrument pack.
