Anti-Theft System (DWA) false alarms

[shogun]

MODEL: 5 Series (E34, E39), 7 Series (E32, E38), 8 Series (E31)
Situation: The Anti-Theft System (DWA) may sporadically trigger false alarms under two specific circumstances, as follows:

(A) Approximately 30 seconds after arming DWA
(B) Sporadically, usually at the same parking location
Cause: (A) Mechanical reverberation of the inclination sensor (NAG).
If a door on the vehicle is slammed shut, the mounting of the inclination sensor (NAG) can vibrate. If the alarm is now armed while the sensor is still vibrating, the DWA Control Module
stores a random reference position. After the normal delay of approximately 30 seconds, the DWA Control Module evaluates the signal from the NAG (which has now quit vibrating) and detects a change of position. This now triggers the alarm.
(B) External electromagnetic radiation that acts on the inclination sensor.

Note:
In both cases, the alarm counter will store the "inclination sensor" as the location that triggered the alarm.
Vehicles Affected: 5 Series (E34, E39), 7 Series (E32, E38), 8 Series (E31) - vehicles equipped with DWA and produced prior to July 1996.

Correction: In the event of customer complaint (only affected vehicles equipped with DWA), proceed as follows:

1. Connect the DIS Tester to the vehicle.
2. E38, E39 vehicles: Under "Body Electronics", select "ZKE" (Central Body Electronics) and then "Anti-Theft Alarm".
E31, E32, E34 vehicles: Select "18 Burglar Alarm System".
3. Select "Service Functions".
4. Select "DWA Alarm Counter".
5. If the majority of entries are for the inclination sensor, identify the index number of the sensor itself (index number is printed on the label of the sensor).
Note:

The NAG is mounted on the left- or right-hand side of the luggage compartment, depending on the model. Refer to the appropriate Electrical Troubleshooting Manual (Component Location).
6. If the inclination sensor (NAG) bears an index number of 10 or lower, it must be replaced with an NAG bearing an index number of 11 or higher.

Note: Depending on the equipment level of the vehicle, the NAG may be mounted behind various accessories such as CD Changer, Cellular Phone Transceiver, etc.
Identify the Index Number by using a mirror (see illustration) before removing the NAG.
Parts Information: Application Part Number Quantity
E31, E32, E34 65 75 8 366 214 1
E38 65 71 8 368 167 1
E39 65 75 8 367 604 1


Warranty Information: Parts and Labor are reimbursable under the terms of the BMW New Car Limited Warranty of 4 years/50,000 miles.
Defect Code: 65 75 20 14 00
Labor Operation: Refer to appropriate Flat Rate Manual
Labor Allowance: Refer to appropriate Flat Rate Manual

original post:
http://members.roadfly.org/smoothy/False%20Alarm.pdf

[pgrindstaff]

Interesting bit of information Shogun. I have a feeling this is what caused me to end up towing my car to a dealership last year. Time to whip out the GT1 interface and see what's going on.