MEMS and the 5AS alarm / immobiliser

[evolotion]

Thought id start a new thread so all the info i have gleaned is in the same place. After much cursing, iv had to admit defeat. the 5as alarm unit cant be bypassed!

There are companies however that can code the ECU so it does not look for the 5as unit, so if you have an engine + ecu + loom but no 5AS, all is not lost! a quick shift through a few google searches should come up with the goods!

However, if your lucky enough to have the above and the 5as, all should be tretty plain sailing. unles you decide to make your own "engine loom" and incorporate the 5AS, as diagrams are scarse.
Tho they do exist 8)

Interesting note : - cars(roughly) post '97 with the 5as have a passive imobiliser, such that the user does not have to press any buttons on the fob, jsu tsimply have the fob near the car. if like me you only have one fob and are skared of looseing it, this is a godsend, as you can jsut gaffertape the fob to the 5AS unit and forget about it! :) the passive bit only affects the imobaliser, the doors etc wil stil only work with buttons being pressed. (asuming you wire the remote locking into your mini...)

IV prety much finished my cut down loom(on paper), il post it when iv seen the engine running with my own eyes! hopefuly this will be of help to people who are useing more modorn donor cars in future :)

[Geehawk]

Any info of this sort will be very useful. As you point out it is scarce.

Keep up the good work!

[evolotion]

Just to add, the passivbe imobaliser stil relies on the batteries! so if your car mysteriously stops running (i.e. starts for a second or 2 then stops) chances are the battery i nthe fob is dead.

with the passive imobaliser, disconecting the main battery wont "arm" the system, as soon as it detects the fob is present it wil automatically dis-arm. where as with the non-passive imobaliser the user had to use the fob or the "key in the door code" to dis-arm after battery removal. This had me stumped origionaly, as i started my donor car, with no battery and a set of jumpleads without any messing with the imobaliser :)

to check if your donor car is "passive", take the fob off the keyring and leave it well away from the car, lik ein your house or something, and try start the car! if ur car has a passive imobaliser the engine shouldnt run for more than a second or 2. then when the fob is brought near the car it should run as normal :)

[picKup]

do you need drawings?
I have acess to the rave cd with all the drawing on!
pm me details and I can post you a copy if you want, but it wont be for a couple of weeks!

Sorry I will not send this to everyone as it will cost lots if I do!

I think it is very hard to bypass!

Mike

[evolotion]

i have aquired the full pinout for the imobaliser unit, cheers fo rthe offer thou :)

o/t however u cud do me a favour and take a pic lookin straight down on ur engine bay :D cheers!

[trickey]

i've just been talking to a guy at my local scrapyard about this, he said to de-immobilize the ecu, you have to plug it into the gizmo that codes the ecu to the 5AS unit, and at the right moment cut a wire (somthing to do with pin 13). then the ECU will spend the rest of eternity waiting for a signal thats never coming, and will work perfectly in the meantime!
He was a bit guarded about specific details,(useful info for car theives!) but seemed to know what he was talking about, I reckon i'll get him to do mine, and report back when I know more.

the idea of cutting a wire to fool the ecu sounds a bit ominous, if the ecu is waiting then while in this state other functions may be disabled, at least you would have to do this every time you start the car, let me know if it works, i have a vtec mini with dta ecu so am not familiar with this, however the 5as has 2 I2c interface cables, comms between these is a standard format, its possible to connect these to a pc via an adaptor, then you can 'listen' to the comms between the ecu and 5as, its not difficult then once you know what code the 5as sends, to build a liitle box with a pic chip in to talk to the ecu on boot up, and make the ecu think the alarm is fitted and disabled, but not having a rover powered mini (yet) havnt done this.

[evolotion]

only problem there is you need the donor 5as to grab thecode as each unit is different. therefore you may aswel just fit the 5as :wink:

you coulds even fit it properly and take advantage of its hideously secure imobaliseing ability... something im contemplating, tho i am very worried about looseing the fob. :oops:

[picKup]

Like you say then, if you fit it, if its not that hard just grab the code aswell!

You always have a back then if you do loose it!

Is it just some sort of square wave?

Mike

[evolotion]

wel yeah it will be a square wave, well. it should be for simplicity. but rover could have been anoying.! it could be anythig from a modulated sine wave(various kinds of modulation amplitude, frequency, phase) or it could be a square wave with more than 2 levels, i.e. not digital.

the pic thing will only work if the code is not rolling btw.

[picKup]

Well I am not sure what it is, but I think it will be simple.
As In dads Emerald ECU you can "learn" a new 5as system then so that it then matches with it like a standard rover ECU.

[evolotion]

really? wel then it must indeed be simple.(relatively)

[picKup]

If your interested have a look at the emerald site http://www.emeraldm3d.com/ its quite good

Mike

yep its a square wave but in blocks of bytes or 8 bits, a start bit is sent (square wave), then the 8 data bits, followed by a stop bit, at the start is a 'block' of bytes which tells the ecu whats going on, getting in a bit too much detail.
its exceptionally difficult to bypass the 5as without the original as the ecu will not 'tell' you the codes, you have to tell the ecu what the codes are, this requires special equipment usually only available to rover, it is possible to get round this with a lot of work but if anyone did, the result could be misused by thieves and make the designer the interest of the cid.
sean.

[evolotion]

iv got a spare stamp controller lying under my bed :P MAY experiment with this in future :) there any more online info on the protocol or is this just your own findings?

[Geehawk]

I think I read somewhere its something to do with ISO 9141, but the search results are all greek to me :?