Stop Light Switch Plausibility

Stoplight Switch Plausibility / Pressure Sensor Zero Deviation
The control module for traction control checks the stoplight switch via the pressure sensor.

Possible Cause(s) of Fault:
- Stoplight switch incorrectly set
- Pressure sensor defective
- Cables between the pressure sensor and control module for traction control are defective

Storage Condition(s):
The fault is entered if the stoplight switch transmits no signal with a brake pressure greater than 15 bar.

Troubleshooting Procedure:
- Slowly press the brake pedal with the engine running until the stoplight switch is activated and observe the brake pressure while doing so. Display of the brake pressure and status of stoplight switch, see Control-module functions
- If the brake pressure is greater than 2 bar, the stoplight switch must be adjusted.
- If this does not succeed, the pressure sensor must be replaced.
- If the brake pressure is less than 2 bar, the cable between the pressure sensor and control module for traction control must be checked.
- If no fault is found in the wiring harness, you must contact the BMW hotline to find out how to proceed.
- Concluding test:
Clear fault memory and carry out the following operation 3 times:
Slowly press the brake pedal with the engine running to shortly before the position where the stoplight switch is activated Hold the brake pedal in this position for 2 seconds.
If fault 69 stoplight switch Plausibility and/or 72 Pressure sensor Zero deviation is then entered, you must contact the BMW hotline to find out how to proceed.

Note:
- Which of these two faults is entered depends on the causes stated and also on circumstances such as speed of pressing the brake pedal.