Sandra Harris

need some advice. My partner has a 2000 clk 320 and left it standing for a while so battery died. He had to change some pump thing in the boot ( sorry, I’m no car expert) and he’s also put in a new battery today as alarm kept going off. The problem is that when he connects the new battery the alarm still keeps going off and now also the front windows are down and can’t go up. Obviously the immobiliser has kicked in so smart key won’t go in. He’s about to lose his rag with this car so really need some advice. Could the alarm be faulty and should he just remove it. Will that fix the immobiliser and window problem or is it something else? I have attached pic of the pump he fitted.

James F

Brave of you for asking Ms Nocarexpert, kind of you to do that for someone else. It may be caused either by a defective key, a failed electronic ignition switch (EIS), a bad shifter module or a bad steering lock module (ESL).

Low battery voltage or sometimes attempting a jump start can cause the EIS to lose its memory. It will not recognise any key if that happens. That is not good news as it (and the other modules if it is one of them) isn't cheap and cannot be reprogrammed easily, except through a specialist electronic auto repairer. Which may or may not work needing a new module anyway.

First off try the spare key, if you have one.

If that does not work then, well I don't think you will like the answer. These cars are so complex only someone with the right equipment will be able to help you properly I think. A good independent MB specialist garage with the correct diagnostic tool is best. Have a look around here, you will see all the threads relating to immobiliser faults ultimately go in that direction
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Lastly, I don't know what that pump thing is you show in your picture. It may be related to you problem but I doubt it and I think it is a distraction here.

Sorry, best advice I can give and more so for it probably being exactly what you did not want to hear. Good luck.