The interior protection system is based on a movement detector (microwaves) that detects movements in the vehicle interior and sends corresponding signals to the ZKE general module.
On the E46 Convertible, there are two interior protection system control units fitted (1 and 2, front and rear); on the E52 Z8, a control unit for radio-controlled surveillance of interior is fitted; and on the E85 Z4 an interior protection system is fitted. The front control unit is located under the centre console behind the gearshift lever/selector lever. The rear control unit is fitted under the rear seat.
A transmitter aerial is integrated in the interior protection system control unit and radio-control surveillance of interior for the purpose of generating an electromagnetic field in the vehicle. The reflections are received by the receiving aerial in the control unit and transferred to the integrated electronic circuitry for evaluation.
Movements in the vehicle cause a change in the reflections and trigger an alarm via the central body electronics control module (ZKE).
For insurance reasons (depending on national legislation), all windows must be closed at all times also when the convertible top is open. This requirement also reduces the risk of a false alarm, e.g. by persons leaning on the car.
Large metal objects (e.g. metal case) shield the electromagnetic waves so that in certain areas no alarm can be recognized due to shadow effects.
When the convertible top is open, an alarm may be triggered in the following instances:
The alarm triggering is stored in the alarm menu of the body electronics control module. A distinction is made whether the front control unit (display: interior protection 1) or the rear control unit (display: interior protection 2) triggered the alarm.
When the antitheft alarm system is armed, the interior monitoring facility is activated by the ZKE general module via the STDWA line and deactivated when the system is disarmed (the same line also activates and deactivates the tilt alarm sensor and siren).
Interior monitoring begins 30 seconds after activating the antitheft alarm system. The interior is not monitored when a vehicle door or the luggage compartment lid is open. Opening the luggage compartment lid or convenience closing of the windows interrupts the interior protection function.
If the interior protection system control unit detects a triggered alarm, this status is signalled to the general module via the INRS or INRS2 (interior protection system control unit 2) line.
In order to avoid false alarms being triggered under unfavourable ambient conditions, the interior protection function can be switched off with the antitheft alarm system activated as follows:
After the anti-theft alarm system has been activated, the interior protection system control unit runs a self test. If a fault occurs here, this status is signalled to the general module of the ZKE via the INRS (interior protection system control unit 1) or INRS2 (interior protection system control unit 2) line. A fault code for defective interior protection is stored in the general module (display: interior protection 1 / interior protection 2).
A faulty module is not activated in order to avoid false alarms being triggered.