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'94 R129 - Immobiliser Replacement

E55BOF

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‘Tis time to continue fettling the SL500. I have come to the suspicion that the occasional bizarre electrical gremlins I have been experiencing are tied up with the (intermittent) fault with the immobiliser.

The car needs a visit to WG M-B anyway, so I’ll get the codes read then, but if the immobiliser does need replacement, what are my options?

I presume the key fob is matched with the immobiliser, so just any old immobiliser unit will not work. Am I right?

Can MB supply a new unit, ready-coded to the car, so that my existing keys work? Or will I need an immobiliser and new keys as well?

I dare not ask how much it will cost….

Or (worst case) is the part NLA?
 
Unfortunately the "MBSS" security setup was UK-specific, installed after the cars arrived in this country. It was an aftermarket system (Scorpion?) rather than M-B, and I doubt it logs fault codes with the car. Fingers crossed for you that it will be fixable!
 
Oh Ferk....

I bought a new key fob from MB soon after I got the car, and was able to register it to the system on the car, so presumably it was pre-coded to work. Is this a cause for hope?
 
If your immobiliser is the same as mine (94 320 SL) It's a very simple device linked to the alarm.

The alarm is armed by using the remote, if the system detects unauthorised entry, it'll prevent the K38 (starter lock out) relay from powering the starter.
The keys aren't coded or chipped. With mine any old key cut from a blank will open and start the car, but only the remote will arm/disarm the alarm/immobiliser.
 
If your immobiliser is the same as mine (94 320 SL) It's a very simple device linked to the alarm.

The alarm is armed by using the remote, if the system detects unauthorised entry, it'll prevent the K38 (starter lock out) relay from powering the starter.
The keys aren't coded or chipped. With mine any old key cut from a blank will open and start the car, but only the remote will arm/disarm the alarm/immobiliser.

Mine is the same; I can open, start and lock the car with the plain key, but what I hope to end up with is a working alarm/immobiliser and remote central locking.

Were the infrared receivers in the doors and bootlid also installed in the UK? If not, what system were they meant to work with?
 
The same system was fitted to US and Canadian models, according to my driver's handbook, so it does look as though it's OE.
 
It may have changed over the years. I've just had a look in my ('97) car and my memory was right - there's an MBSS installation certificate stating it was fitted in the UK by Scorpion Security Systems, and the vehicle owner is given as MB UK. It's dated about 10 days before the car was first registered.
 

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There are a number of confusing combinations of car+aftermarket alarm/immobiliser combos depending on age.
1. cars with no remote central locking/ immobiliser/ or alarm--- for these aftermarket alarms can provide all three functions depending on how they are wired up but the remote will be after market also NOT Mercedes.
2.cars with a Mercedes IR remote locking system [ usually identified by the flip type key and a drivers door with no lock for a key just a red/green led in the handle.] For these the alarm can provide immobiliser/and alarm functions . These keys can be coded by Mercedes.
3. cars with an IR Mercedes remote locking system and immobiliser as above [.........]. the alarm is normally just an alarm. [keys can be coded by Mercedes]
4. Cars with a Mercedes remote locking system immobiliser and alarm from factory no aftermarket unit required keys can be coded by mercedes and usually now multi button and possibly both RF and iNFRA RED.

So gradually as Mercedes provided more functions aftermarket alarm functions decreased. At the same time Mercedes factory remotes got more complicated with more buttons more modes of signalling.

Think I got that right?? :confused:
 
It looks as though I have Type 2, but with key locks as well as the sensors on both doors and the boot. The boot lock, however, is not (and never has been) wired to operate the central locking on the key, but both doors are, and do.

If I lock the car with the fob, the alarm, immobiliser and central locking are all activated.

If the remote system then decides not to play when I try to unlock the car with the remote fob, I can use the key to open any of the locks and turn the ignition on as normal, but the alarm sounds and the car will not start.

The fob that came with the car is u/s, so I bought a new fob/flip key from MB. It works as it should.

I think a Star session is the next step...
 

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