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RV8 alarm resynchronization - not alarm ECU damage
A posting on the V8BB by Peter Steyn (Woodcote Green 1678) from South Africa is a useful tip solving a "damaged" Alarm ECU unit. (Jan 06)
RV8 "plip" for activating the alarm ECU. (Image: RV8 Owner's Handbook)

I have 'solved' what I initially thought was a damaged Alarm ECU unit after trying to start a car with a flat battery. Possibly others with the same problem could benefit from this simple remedy. Reading through my Owner's Handbook AKM7144, I stumbled on a paragraph on page 12 under anti-theft alarm subtitled "Using the


Note on synchronisation on page 12 of the RV8 Owner's Handbook

Handset" where it describes having to resynchronize the handset if arming or disarming attempts are out of range - typically you are too far
away from the car when pressing the handset button. It describes the handset as transmitting a coded radio signal, which changes every time the button is pressed and if an attempt is made out of range, synchronization between car and handset is lost. The remedy to resynchronize the system is to stand close to the car and to press the button 3 times in quick succession within one second.

From what I can figure out, and still as guess at this stage, is that after my battery ran flat on my car, synchronization must have been lost in the alarm system and that any attempt to arm the alarm thereafter simply produced no effect at all - the LED light on the handset illuminates on depression, but the hazard warning lights on car do not illuminate signalling the car is armed. After the resynchronization remedy, my alarm system is now working fully as before.

David Sutcliffe followed that posting with "thanks for the tip. I have disconnected battery and recently installed a new battery. Not sure when the alarm stopped working but only noticed yesterday it would not turn on. Did as you said and it is now fine".

Brian Moyse (BRG 1714), who prepared RV8NOTE191 on the risk of damage to the alarm ECU if the battery runs down if the car is not used for an extended period, typically during the Winter months, has commented that in his experience with the RV8, loss of synchronisation between the key and ECU codes is a frequent occurrence in normal use. In his case it occurs most often because he carries the key and alarm fob in a trouser pocket and occasionally accidentally presses the button (which is quite sensitive) when away from the car, either by his leaning against something or often through knocking it when his hands are in his pockets. It can also happen if, for instance, you try to arm the system with a door not closed fully or the boot lid not securely locked. If you have studied the handbook, you would try this first in the event of the alarm not arming, before concluding that the ECU was faulty.

In RV8NOTE191 the difficulty he was referring to was a more specific "terminal" failure of the ECU and suggesting a possible cause. Brian went through all the tests - for example fob synchronisation, putting it on an MG Rover Testbook (which could not communicate with the ECU and at which point the MG Rover dealer gave up) and finally having a specialist vehicle electrical company do an input/output check which confirmed the diagnosis.