I have recently obtained a 2001 ML430 that seems to have an odd problem with the remote locking. The inside switch works perfectly in both directions(lock,unlock), and all the doors can be locked manually, and the outside locks work with the key, except they only all unlock electrically. The remote doesn't work, except for one time after I resynchronize it. I put new batteries in and it does the same. I re-sync and I can lock once, then re-sync and unlock, and re-sync and unlock rear hatch. I can even wait for 30 min or so and it will still work perfectly(any one button) ONCE even from 40ft away. I only received one key with this, since it was kind of a rescue from a barn, so I can't tell if it is the key or a sync problem. I know this is supposed to have a rolling code, and to me it seems like it isn't rolling on one end or the other. Has anyone had this problem? I've been a Jag (and other British)mechanic for over 40 yrs. but they don't have anything like this, so I'm hoping I can get some help. Thanks for any help. Denny

 

hope you found a trick by now. took me a while to get my remote to work. found an old post that mentioned fuses. I checked the fuses & in my trunk there was one burnt out & one missing that were numbered for the central locking system. changed the fuse & added the missing fuse & so far I can lock my car in the daytime!- the remote had only worked at night. it's a major hassle to manually lock my beautiful car - so now I'm happy - good luck

 

I know this is rather an old thread, but I have exactly the same issue as the OP.

I also have a 2001 ML430, and I also get one shot at locking/unlocking with the remote after a resynch. (I've also only got the one remote, hoping to take care of that soon.)

I'm going to check the fuses as suggested by the 2nd poster. Thanks for the hint.

 

well, my intermittent locking/unlocking is happening again. my mechanic replaced the batteries hoping that would do the trick. but as you know there is something else happening with the laser/eye remote key! mine locks/unlocks at night like a charm. my 2006 E350 is in the shop for a "squeeking" noise, so maybe the mechanic will check again - since this time I told him the key works great at night.
stay tuned

 

sounds like ur ml needs an aam (all activity module). when this goes bad your locking snd unlocking of the car will malfunction.

 

exact same prob with with a 2000 ML270CDI, shall check the fuses, then I guess if that's not it an AAM!, or maybe I'll just lock up manually