Suspected Immobiliser fault

[buggymart]

I have a 1994, E220 saloon (last of square shape) which turns over but does not fire. It is fitted with an immobiliser that may not be factory fitment - it is activated and deactivated by aiming the keyfob at red/green light on drivers door or boot. The central locking all still works fine, the red light in key fob lights if centre button held in suggesting batteries ok in fob but engine does not fire. This happened about 5 years ago and car went in to local Merc dealership who from memory said they had fitted a new "computer". Can anyone give advice on where to start looking for the cause please or how to bypass the alarm

Thank You

Buggymart

 

[roofless]

turn the ignition on & if you dont hear the fuel pump run it might be just a relay fuel pump relay or ovp relay both are behind the black plastic cover at the battery

 

[dragon]

I have a 1994, E220 saloon (last of square shape) which turns over but does not fire. It is fitted with an immobiliser that may not be factory fitment - it is activated and deactivated by aiming the keyfob at red/green light on drivers door or boot. The central locking all still works fine, the red light in key fob lights if centre button held in suggesting batteries ok in fob but engine does not fire. This happened about 5 years ago and car went in to local Merc dealership who from memory said they had fitted a new "computer". Can anyone give advice on where to start looking for the cause please or how to bypass the alarm

Thank You

Buggymart

It got a security alarm fitted as standard unless it had been modified or replaced. If you unarmed it and the red light it on means something is not right.

Check the fob batteries and synchronise the key with the system. If it is still not OK then it the immobiliser, get it diagnosed. Try the spare key if you got one.