Installation Procedure

Figure 1.:

In order to verify which alarm ECU is installed in a car, remove and reinstall the alarm system fuse (fuse 22 in early M89 cars and fuse 19 in all others). Close the driver's door and then turn and hold the key in the unlock position for at least 10 seconds. If the car is equipped with the new design ECU, the siren will chirp and the parking lights will flash. If nothing happens after holding the key in the unlock position for 10 seconds, then the car is equipped with the early design ECU.


2. In order to replace the alarm ECU, the glove box must be removed (see Service Manual Sec. 8:3, P.854-13). The ECU is mounted on a metal bracket that has four retaining feet which secure the ECU. It is extremely important that all four mounting feet are secured and the two locking fingers are fully engaged in the groove on the base of the ECU (Figure 1). An incompletely fastened ECU will be prone to false motion detector alarms.
3. Instead of removing the glovebox, some technicians may be tempted to install the alarm ECU with the limited access gained by removing the sound insulation panel under the dash. However, because the ECU is not clearly visible from under the dash, this method carries an unacceptable risk of incorrectly mounting the ECU on the bracket. Always gain access through the glovebox when removing and replacing the alarm ECU.