Immobiliser Problem?
After a long period of being really good, my G500 (1999) has decided that it doesn't want to start!
Turn the key to first position and all dash lights come on as usual; turn the key further to start and nothing..... not even a buzz from fuel pump. The battery is in good nick but what does happen is that the red/green lights on the interior mirror flash alternately. Normally the red one flashes briefly when locking the car and the green one when unlocking but never both together. The manual helpfully says if both lights flash "consult your MB dealer"! I have a suspicion it may be an immobiliser fault - does any one have any ideas please??
It's not the immob but you have a problem. What are you like with vehicle electrics, circuit diag and testing?
It could be something simple like the gearbox lockout, have you tried moving the gear selector slightly? P and N will allow to start.
Try re syncing the key...does the spare do the same?
The immob and central locking are independent systems. The immob disables the fuel system but allows engine cranking. You have a different problem. It;s ecu related, it could be the K40 relay which provides the power. You need to be able to test the voltage at different terminals.
I guess you have a 'normal' ignition key and not one of the new infra-red ones?
have you tried the spare key, if you have one?
the immobiliser used a high-frequency transducer coil around the ignition key lock and communicates with an RF-ID device inside the key. If the spare-key also does not work , it may be a problem with the antenna ring around the ignition switch or the immobiliser control unit.
Tried the spare key this morning and car started perfectly as if nothing had happened........ The original key and the 'credit card' style emergency spare also now work.
I'm relieved but also frustrated by this result as it puts the thought in my mind that there may be an intermittent fault which will no doubt re-emerge at the most inconvenient time!!
Thanks for your responses; next time I'm in Inverness I may ask MB to run a diagnostics check to see if anything shows up.
Good news. The K40 relay provides power to the ecu. It develops an intermittent fault with age and can be fixed by resoldering the joints or replacement of the relay. It sounds like you have had the first indication that yours is going bad.
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Thanks guys for your replies. Have tried moving gear lever including into neutral but no joy. Will be trying spare key tomorrow as I had to leave Wagen at friend's house and get lift home.