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Mpi Alarm/immobiliser

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#1 leepol83


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Posted 22 September 2020 - 08:29 PM

Hi chaps just a quick one how does the standard alarm/immobiliser actually work on the mpi mini, how do I arm alarm etc sorry if this sounds stupid but I haven’t got a manual for the car
I’m under the impression you put the key in turn it once and press unlock on the fob, this de immobilised the engine and will start, once I’ve driven it and taken the key out do I need to press the fob to set the alarm/immobiliser Once I’ve locked the car ?
Thanks sorry if it’s a stupid question

#2 RedRuby


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Posted 22 September 2020 - 08:46 PM


#3 Quinlan minor

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Posted 22 September 2020 - 09:24 PM

My MPi self armed until I got it re-programmed.

As below:

Don’t Panic, Captain Mainwaring!

There’s some cause for alarm.


Although I’m extremely fond of my 1998 MPi, it has one irritating feature which, even after six years, still catches me out from time to time.


The alarm/immobiliser, an MG Rover 5AS, has what’s called “passive arming” and it operates by disabling the fuel pump. The effect is, in my opinion, potentially quite dangerous!


Picture the scene: you pull up to pick up the wife/kids (in your designated role of transport manager) on the side of the road, switch off and wait. Eventually they turn up, get into the car, you start up, pull out into a gap and the engine cuts out! “Damned immobiliser!”


To restart, you must push the arm button on the remote,  then wait twenty seconds or so until it resets itself.


Twenty seconds seems an eternity when a truck is bearing down on you!

You then hit the disarm button, restart the engine, and get on your way, grumbling like Muttley from ‘Wacky Races’.


Recently my problem was made considerably worse, when the ability of the transmitter fob to disarm became erratic.

 Sometimes it would take fifteen or twenty presses to work and, invariably, the more I was in a hurry, the longer it took.


Unfortunately, only one fob came with the car when I bought it, so I couldn’t tell where the fault lay, with the transmitter or receiver.


I changed the battery, it seemed to work until an early start Monday morning.

I checked the fob circuit board and found a dry joint. Re-soldered it and it seemed to work until …..

Took the receiver out, checked it for damp ( a common problem caused by a leaking windscreen) no problems found. Replaced it, seemed to work. You’re probably ahead of me by now.

Unfortunately, the way the 5AS works is by sending a discrete code to the engine management unit, so you cannot simply bypass  the bloody thing!


After some research, I was lucky to find Paul Brown at Technozen Electronics.

Paul has all the kit and will supply two new fobs coded to your 5AS ECU at a very reasonable price.

He can, also, disable the passive arming, match your 5AS to a replacement engine ECU. R Clone your 5AS details if you want to fit the "later" type 5AS to add indicator flash on arm/disarm, or reprogramme the Engine ECU to remove the immobiliser.

Normally, you send the unit with any old fobs to him, by post, and he will return them to you within one working day. As my car is a ‘Daily Driver’, he was kind enough to sort mine out while I waited, parked on his drive.

I now have a spare fob (I’ve had a spare set of keys cut, too), the range on which is better than my old one ever was.

Paul can be contacted:

[email protected]

 44 Meadowview



East Sussex


07527 877995



#4 leepol83


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Posted 23 September 2020 - 07:25 PM

Wow!! Thank you for that I’ll make contact and see what he can do thanks again really appreciate that.

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