Lighting Systems - Overview - E38, E39 & E53: Overview BMW 7 series E65/E66

Model: E38, E39 and E53

Production: Start of Production MY 2004

Emergency Operation

If there is a failure of the LCM processor, an emergency circuit is activated within the LCM. This will allow the following lights to function for driving safety

1. Side marker/tail lights
2. Low-beam lights
3. Brake lights
4. Turn signals

In emergency operation the following lights will not operate

1. Dimming control (full bright)
2. Hazard lights
3. High-beam lights
4. Headlight flash
5. Fog lights
6. Back-up lights

The I-Bus/K-Bus communication to the LM will also be interrupted.

Version Identification

Xenon systems on BMW vehicles are supplied by two manufacturers - Bosch and Hella. These systems vary between models.

The first version system on the E38 is referred to as Generation 2.1 an can be identified by the flat bottom edge on the headlight housing.

The Generation 3 system has been introduced on the 1999 model year E38 and can be identified by the rounded (scalloped) edge of the headlight assembly.

Phases Of Bulb Operation

1. Starting phase - the bulb requires an initial high voltage pulse of 18-25 kV to establish the arc.
2. Warm up phase - Once the arc is established, the power supply to the bulb is regulated to 2.6 amps generating a lamp output of 75 watts. This is the period of operation where the xenon gas begins to brightly illuminate. The warm up phase stabilizes the environment in the bulb ensuring continual current flow across the two electrodes.
3. Continual phase - once the warm up phase is completed, the system switches to a continuous mode of operation. The supply voltage for the bulb is reduced and the operation power required for continual bulb illumination is reduced to 35 watts which is less than a conventional halogen bulb.

Functional Description

To regulate the power supply to the bulbs, additional components are required. The xenon control modules (1 per light) receive operating power from the LCM when the headlights are switched on.

The xenon control modules provide the regulated power supply to illuminate the bulbs through their phases of operation. The igniters establish the electric arcs. Integral coils generate the initial high voltage starting pulses from the control module provided starting voltage. Thereafter they provide a closed circuit for the regulated power output from the

Scheme 53

The E38/E39 LWR system comes on-line when the lights are switched on. The LWR control electronics then cycles the stepper motors through their full range of motion and stops at a default position.

The control electronics monitors the level sensor input signals to determine the vehicles load angle and adjusts the beam position accordingly. As the vehicle is driven it continually monitors the level sensor signals and if necessary updates the headlight beam positions every 25 seconds on the E46 or momentarily on the E38/E39 system.

Abrupt fluctuations of the sensor signals are filtered to prevent unnecessary adjustment as well as monitoring road speed and brake pedal application as correction factors.