Parking brake
Check the pressure monitor circuit for shorts and breaks. The signal on coordinator pin 20 (on earlier models of coordinator) or on pin A23 (on later models of coordinator) should be high (+24 V) only when the parking brake is applied.
What you'll see
No driver-visible symptom recorded.
System reaction
No system-reaction text recorded.
Diagnostic depth
The signal from one of the pressure monitors for the parking brake circuit has been implausible in relation to the vehicle speed. The parking brake circuit has one pressure monitor which monitors a high air pressure, and one which monitors a low air pressure. This fault applies to the lower pressure.
The pressure monitor has indicated that the air pressure in the parking brake circuit has been below a certain value, and is has thereby opened the circuit to the coordinator. This is interpreted as the parking brake being applied, and at the same time the vehicle speed has been above 30 km/h. This may be because the pressure monitor circuit has been shorted to earth.