Motion Sensor Problem

[alxy]

Hi bros,I have a 2001 E46 325 fitted with motion sensor alarm. Trouble is, nowadays, it seems to be tripping for no apparent reason, particularly when it is sunny. Firstly, I assume it's the motion sensor, as I can't think of any other alarm being tripped. Manual says to press the lock button twice to disable motion sensor. I tried that (press twice slowly, price twice quickly, whatever speed and combination), still doesn't work, i.e. alarm still trips. Or could it be some other contact wire being loose? But that is a bit unlikely as when parked in my porch (i.e. no sun), it doesn't trip. Only when out in the direct sun. Heat sensor? Don't think that exists....or does it? Anyone face this problem before? Any solutions? Or any way to just remove the dang thing?Thanks!

 

[jarance]

According to BMW WDS.

Ultrasonic Interior Protection
The ultrasonic interior protection system is based on a movement detector that detects movements in the vehicle interior and sends corresponding signals to the ZKE general module.

Function
Ultrasonic module
The ultrasonic module contains the electronics and ultrasonic sensors (transmitter and receiver). It is installed in the headlining in the centre area of the vehicle. Two pairs of sensors (transmitter and receiver) monitor the entire vehicle interior.

Movements in the vehicle interior are detected in that the reflections of the ultrasonic waves (echo) change. The ultrasonic module then signals an alarm triggering to the general module.

Arming/disarming
When the antitheft alarm system is armed, the ultrasonic interior protection 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 arming the antitheft alarm system. The interior is not monitored when a vehicle door or the boot (trunk) lid is open. Opening the boot (trunk) lid or convenience closing of the windows interrupts the interior protection function.

If the ultrasonic module detects a triggered alarm this status is signalled to the general module via the INRS 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 armed as follows:

Arm antitheft alarm system via door lock or remote control

Repeat arming procedure within 10 seconds

Self-Test
After being armed, the ultrasonic module carries out a self-test. If a fault occurs, it is signalled to the ZKE general module via the INRS line. A fault code for interior protection is stored in the general module.

The following faults can be detected as part of the self-test. Module electronics faults, sensors interrupted, sensor short-circuit, sensors covered over, INRS line faulty.

A faulty module is not activated in order to avoid false alarms being triggered.

According to the above highlight, you have to arm it twice within 10 seconds. Since you try the procedure with remote key and it does NOT work, maybe try it with the key.

 

[alxy]

Thanks bro jarance. Now actually I'm not sure if indeed it was the motion sensor. So perhaps the disabling with the remote by pressing twice did work after all. What happened is I took out the motion sensor by unplugging it. But still the problem occurs. Not sure if unplugging the motion sensor is causing the problem now, or it never was due to the motion sensor in the first place. Have to diagnose more. Any more ideas, anyone?

 

[moots]

on the e39,the common iproblem about the alarm triggering when parked in the sun is the bonnet sensor/switch.it's an adjustment issue.try disconnecting the connector from the switch and see.if it stops triggerring,then you have an adjustmnet issue.simple fix.perhaps this applies to the e46 as well.the bonnet sensor/switch on the e39 is at the lh strut tower

 

[jarance]

A faulty module is not activated in order to avoid false alarms being triggered.

If you disconnect he module, it is considered as a faulty module and will disable the motion sensor.

Since you are still getting alarm, it could be the bonnet switch as pointed out by moots.

or the boot switch or one of the doors switch..

 

[alxy]

Thanks bro moots and jarance,

I took out the bonnet sensor and so far problem seems to have gone. Will monitor for a while more to confirm.

 

[alxy]

Just to close off this topic. After 1 month of testing, it appears to be the bonnet sensor. Have put some tape strategically placed to ensure sensor is closed tightly once bonnet closed. No more false alarms since. By the way, moots said E39 had same issue, and my E46 also the same. Wonder if this is why BMW just forgot it altogether for the E60? I cannot seem to find a bonnet sensor on my E60.

Cheers!

 

[jarance]

Extract from BMW WDS.

1 switch for bonnet light and the other for alarm.

 

[alxy]

So there is a bonnet sensor, hidden somewhere inside. From the pics, appears to be may positions it can be. Will check out which one it is. Thanks bro!

 

[alxy]

Hmm....looks like mine is similar to the second picture above, except that the housing is there but there is no sensor. Anyway, no biggie.....