Discovery II
BODY CONTROL UNIT
86-3-32 DESCRIPTION AND OPERATION
The shift interlock option can be programmed in one of three states dependent on market/ customer requirements,
these are:
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Option 1– not fitted.
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Option 2 – normal operation.
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Option 3 – inhibit transfer box.
The BCU checks the status of the following inputs to determine the logic action for employing the shift interlock
solenoid:
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Brake switch activated.
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Ignition state.
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Gearbox state.
In the event of a communications link failure, the shift interlock solenoid enable is switched on for 1 minute every time
the ignition is switched on and switched off when the ignition is turned off.
Ignition interlock (where fitted)
On automatic gearbox models, when the ignition key is inserted in the ignition switch, the ignition key-in switch
contacts close to supply a signal to the BCU to indicate the presence of the key in the switch and provide a supply
feed to the ignition interlock solenoid. If the gear selector lever is in a position other than Park, or the 'transfer box
neutral selected' is on, the BCU will supply an earth path to complete the ignition interlock circuit and cause the
interlock solenoid to be engaged. With the interlock solenoid engaged, removal of the ignition key is prevented. The
BCU will open the circuit, to allow removal of the ignition key, only when the gear selector lever is in the Park position
and the transfer box is in either high or low range.
The ignition key interlock option can be programmed in one of three states dependent on market/ customer
requirements, these are:
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Option 1– not fitted.
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Option 2 – normal operation.
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Option 3 – inhibit transfer box.
The BCU checks the status of the following inputs to determine the logic action for operating the ignition key interlock
solenoid:
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Transfer box neutral selected.
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Gearbox state.
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Transit mode.
When the transit mode is on, the ignition key interlock solenoid is off.
Transfer box interlock (where fitted)
The transfer box interlock is controlled by the IDM to prevent transfer box shifter operation unless certain
preconditions have been satisfied.
The transfer box interlock prevents the transfer box being shifted from High or Low to neutral with the ignition key
removed from the ignition switch. When the BCU senses that the ignition key is removed from the ignition switch, it
signals the IDM via the serial data bus. The IDM then provides an earth path for the coil of the transfer box relay,
energising the relay coil and closing the relay contacts to provide a voltage supply to the transfer box interlock
solenoid.
A diode is included in the supply line to the solenoid to prevent residual current causing the solenoid to stick in the
energised position.
The transfer box solenoid interlock option can be programmed in one of three states dependent on market/ customer
requirements, these are:
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Option 1– not fitted.
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Option 2 – normal operation.
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Option 3 – inhibit transfer box.
The BCU checks the status of the following inputs to determine the logic action for employing the transfer box interlock
solenoid (transfer box solenoid enable):
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Ignition state.
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Gearbox state.