Immobaliser - W202 C280

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Mr Gee

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Aug 4, 2003
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Location
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Hi All

Drove to work today no problems - trying to get home now and the car wont start.

Its a 1995 W202 C280 Auto. I can lock and unlock the central locking via the remote fob but cant start the engine. The engine turns but wont fire.
The alarm system I have is the type thats built into the rear view mirror with a green and red LED. I have noticed that when I arm the alarm, the central locking engages, a get 1 flash from the green LED but the red LED does not flash to show that its armed itself. If I unlock the car and turn the ignition to get the all diagnostics light on the dash, I notice the green LED in the mirror continously flashing for about 20 seconds.

I have tried removing the earth cable from the battery for 15 minutes to see if anything changes but its still the same and all fuses are intact. - I also do not have any door locks to get into the car via the key. Its all done via the remote fob.

Has anyone come accross this before ?

Any suggestions ?

Many thanks

Gee

:confused:
 
I think i have the answer for you.

Remove the interior mirror and re-solder a new red LED on to the printed circuit board inside your mirror. The mirror housing comes apart enableing you to acesss the blown LED.

A new led is available from maplin.
 
Hold the keyfob button down, how bright is the red LED that is visible? (on the keyfob itself)

Very low power in the keyfob wont allow the car to start.

Does the central locking still work when you lock it?

Have you tried another keyfob?
 
no red LED in the interior mirror will stop the car from starting. problem is with these mirrors older types have a bulb in them which flashed all night when the alarm was set consequently blowing the bulb. New mirrors supplied by Merc now have LED's instead of bulbs to cure this problem.
 
The Red Bulb In The Mirror Is Part Of The Imobiliser Circuit As Is The Red Led In The Drivers Door Reciver , One Of These Bulbs Blows You Have No Problem But When The Other One Blows , You Cannot Deactivate The Imobilser Circuit, Get One Bulb Circuit Working And It Will Start,

Also If Key Fob Batterys Are Low The Red And Green Light Flash Together. Change Batterys


You Can Bridge The Alarms Circuit Out By Remove The Metal Kickplate Behind Passenger Floor Carpet

Pm If You Need Colour Of Wires To Bridge:)
 
- I also do not have any door locks to get into the car via the key.


:confused:[/QUOTE]

I think you do have a key lock on the passenger door handle, it might be hidden behind a removable black plastic bung about the size of a penny, that’s the way it is on mine. I might be wrong but worth checking.

Dec
 
- I also do not have any door locks to get into the car via the key.


:confused:

I think you do have a key lock on the passenger door handle, it might be hidden behind a removable black plastic bung about the size of a penny, that’s the way it is on mine. I might be wrong but worth checking.

Dec[/QUOTE]

Yep looks like you've got a lock cover fitted

merc9.jpg
 
Thanks Hi-Lo, a picture speaks a thousand words.
dec
 
Sorry for the delay in responding back -

First of all - thanks for all of you who replied back with yiour suggestions.

I got kicked out the office and so had to go and wait by the car for an electrician friend of mine.

Anyhow, my buddy spent the good part of 4 hours trying to resolve the issue.
He tried all your ideas, which all failed and in the end he spliced into the wiring behind the passengers footwell to bypass the immob - its not something he wanted to do but was a last resort. It managed to get me home - :rolleyes:

BTW, the passenger door had a blanking plate over the lock and managed to remove it, but this didn't achieve anything when I tried to enter the car via the lock. Also tried re-synching the fob which had new batteries in it - nothing doing.

Definate fault in the immob circuit somewhere as when you sit in the car and arm the system the siren does not go off and neither do the motion sensors flash to show movement if you open the door after a minute.

- If you are saying that the red bulb or red LED in the rear view mirror is part of the immob circuit, then I well get this checked out and replaced. Its not something we looked at. Can anyone confirm this. ?
 
Get the LED replaced. Hopefully it will solve all your problems.

It is somtimes difficult to diagnose somthing over the web but this is my best suggestion for you. The LED is part of the alarm circuit.

Get your electrician friend to replace it for you
 

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