The warning light also lights up if the transport lock has been activated via the diagnostic module.

The level sensor

The following parameters can be measured with the aid of the level sensor:

Vehicle inclination

Transverse acceleration

Longitudinal acceleration

The level sensor consists of the following

Spirit level housing which is filled with fluid and contains an air bubble

Light-emitting diode (LED) (sender function)

Phototransistor (receiver function)


1. Spirit level housing

2. Air bubble

4. Phototransistor (receiver)

5. Mirror

If the vehicle exceeds the set limit values during transverse or longitudinal acceleration or pitches around the longitudinal axis by more than the limit value, the air bubble passes through the visual send and receive section. This movement of the air bubble is detected by the receiver and the system is triggered.

Gravitation sensor (g-sensor)

The g-sensor is used to detect driving situations in which the vehicle loses contact with the ground (e.g. jumping over a bump).

The g-sensor function is based on a spring/weight system. As a weight, a magnet which counteracts the spring force with the force of its weight is used.

If the vehicle lifts up from the ground, the magnet becomes lighter and the spring can press it upward. This closes the reed contact and triggers the system.

Roll-over protection system diagnosis

911 Carrera (996)


1. Weight

2. Magnet

3. Compression spring

4. Reed contact

69 71 Diagnosis/troubleshooting, roll-over protection system


Printed in Germany -11, 1998

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