Tail Lamp: Description and Operation
9431 Rear lights
Particular attention has also been paid to the new night-time design of the 911 Carrera when it comes to the rear view. The tail light, always very narrow on previous models, now extends across all three tail light chambers and so continues the night-time look. The bulbs in the rear lights are produced in long-life quality.
On left-hand drive vehicles, the rear fog light is located on the outer left side of the redesigned rear light (on the right side on right-hand drive vehicles).
The centre high-mounted brake light is executed using LED technology and has been adapted to the new design of the rear lid. The wide rib in which the brake light is housed acts as an additional design element for the air inlet on the rear lid and so blends in seamlessly with the styling of the rear area. As on the previous model, there is a second brake light unit integrated in the rear spoiler to ensure visibility when the rear spoiler is extended.
The new LED technology has a number of clear advantages in terms of service life and response time. The response time of bulbs is around 100 ms. LEDs respond after around 0.1 ms. This difference translates to a distance of almost 3 m at a speed of 100 km/h. Earlier indication of an intention to brake means more time for other drivers to react. LEDs also have a considerably longer service life (generally in excess of 10,000 hours) than conventional bulbs that need to be replaced after only 200-1000 hours.
Brake light switch
The PSM control unit identifies a brake light request from the redundant switch combination consisting of "brake light switch" (BLS) and "brake test switch" (BTS). The PSM control unit also checks the sequence of opening/closing operations performed by these switches for plausibility.
The brake test switch must open first when actuated, following which the brake light switch must close after a short delay.
NOTE: The brake light is activated directly via the brake light switch. The rear control unit activates the brake light on the right and the 3rd brake light.
The PSM control unit relays this information via CAN Drive and passes on the messages to the Motronic control unit.
In parallel with the PSM control unit, the rear control unit and the driving authorisation control unit (Porsche Access System - PAS) read in the signal from the brake light switch.
Light failure monitoring
Most exterior lights are equipped with a failure checking facility. In the event of a problem (e.g. bulb failure, wire defect), a corresponding message is displayed in the instrument cluster.
The following lamps are monitored:
- Dipped beam
- High beam
- Marker light
- Indicator light
- Brake light
- Rear fog light
- Reversing light
In case of lamp failure during "ignition off", the fault is stored and subsequently transmitted via CAN in conjunction with the next "ignition on" cycle. The lamp failure checking facility is not active during "sleep mode. In case of lamp failure during "ignition on", the fault is transmitted directly.