Body control unit (Courtesy headlamps): Description and operation

Courtesy headlamps

This feature activates the headlamps for 30 seconds when the lock button on the remote transmitter is held down for longer than 1 second. The headlamps will extinguish if the BCU receives either a lock or an unlock signal from the remote transmitter.

The BCU checks the status of the following inputs to determine the correct qualifying conditions for requesting courtesy headlamps: l Ignition state. l Remote locking request. l Remote unlocking request. l Lazy locking request.

If the ignition is off and a lazy locking request is received, the courtesy headlamps are switched on and an internal timer is turned on in the BCU which operates for 30 seconds. If the 30 second timer expires or a request for remote locking or remote unlocking is received, the courtesy headlamps will be turned off.

When main beam is selected, the IDM also provides a signal to the instrument pack to switch on the main beam warning lamp. An additional signal 'main beam indicator disable' is used to prevent the daylight running lamps illuminating the main beam indicator when the main beam is in the daylight running lamp state and the main beam indicator disable signal is on.

Lights on alarm The lights on alarm in the instrument pack operates when the driver's door is open and the side lamps or headlamps are on. The system uses inputs from the driver's door switch and the lighting switch to determine the logical conditions that need to occur for switching on the alarm. The BCU carries out the logic operation and communicates with the instrument pack using the serial data bus; the instrument pack will be requested to sound the alarm if the logic inputs indicate that the driver's door is open with the lights still on.

Supply voltage is provided through the lighting switch to the IDM which acts as the signal line to indicate that the lights are on for the logic circuits in the IDM and BCU. When the driver's door is opened, a second feed is supplied to the BCU through the driver's door switch to indicate the condition. In this logic condition (lights on and driver's door open) the BCU signals the instrument pack to operate the audible warning. If the lights are switched off or the driver's door is closed the logic condition will be changed and the audible warning will be switched off.

Daylight running lamps

The BCU operates the daylight running lamps (where fitted) via the IDM. The daylight running lamps option can be programmed in one of three states dependent on market/ customer requirements, these are: l Option 1– no daylight running lamps. l Option 2 – on with main beam off. l Option 3 – on with main and dipped beam off and gearbox not in Park.

The BCU will ensure the logical conditions are satisfied for the lamps to operate under the set conditions. The BCU checks the status of the following inputs to determine the logic action for providing an output to the daylight running lamp relay: l Main beam state. l Engine running (link from instrument pack). l Dipped beam. l Gearbox state.

A voltage supply is fed to the coil of the daylight running lamp relay and the IDM. When the preconditions are satisfied for daylight running lamp operation, the BCU sends a signal for the IDM to complete the circuit to earth to switch on the daylight running lamps. The logical inputs are checked to ensure that the engine is running before switching the relay to turn on the daylight running lamps. The engine running signal has to be present for at least 2 seconds before the daylight running lamp relay can be switched on.