Detailer description: General

The courtesy lamps are activated by the respective door module via bus messages from BCM (Body Control Module). Luggage compartment lighting is activated from the Rear Electrical Centre (REC) also via a bus message from BCM. Other lamps receive their power supply from a relay activated by BCM. The lamps are grounded with PWM (pulse width modulation) from BCM or receive a direct ground from the body via a button or switch.

All interior lighting, including courtesy lights and luggage compartment lights, go off automatically after 20 minutes unless the ignition is turned on. BCM activates the relay and sends the bus message that the luggage compartment lighting and courtesy lights should be turned off.

Lamps are turned on by buttons when the relay is not activated, e.g. if you remain in the car for 20 minutes without the ignition on. In this situation, if you press a button to turn on the roof light or a reading light, open the glovebox or turn on the vanity mirror lamp, BCM will activate the interior lighting relay for a further 20 minutes. The lead from the relay passes through BCM enroute to the lamps. BCM applies a voltage and measures the lead to assess whether the circuit is grounded by a button or switch when the relay is not activated.

Note that BCM only detects a voltage drop when a button suddenly grounds the circuit. BCM cannot detect whether the interior lighting has been activated e.g. by the glovebox being already open.

The car interior lighting consists of the following: