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Discussion Starter #1
I have keyless-go on my 2005 CL55. I have 2 set of remote keys, one for spare. The last time I used the spare it worked fine.

The last week or so, I noticed when starting the car using the button on the shiftknob, it said "check key battery" (on my regular using key) but everything still worked.

I went ahead and replaced the battery yesterday. When I came out of the car and started it, it still said "check key battery" with the new battery.

Went to see a movie last night and when I came out, the remote would not open the door. I used the key blade to open it and alarm went off. I inserted the key into the ignition and started the car fine. The key is no longer lock/unlock the doors.

I took out my 2nd (spare) key and tried, same problem. The whole time I was pressing the buttons, I was able to lock the car once with the 2nd key.

Any idea what went wrong? Thanks for reading.
 

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Only time ive had trouble like this is when i left my lights on and battery went flat overnight sounds like the alarm system
 

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you check the batteries on the key fob? car battery running low would do the same, be sure your battery on the car is at proper level and you have fresh ones in the key fob :thumbsup:
 

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Had the same issue

The problem isnt the key fobs its the sensor under the headliner at the back window which picks up the information from the key. I bought a used one at the junk yard for 75.00 and put it in myself in about 20 minutes and now I can use my remotes again. Also, it could be your handle is bad. You will have to take it to the dealer and let them diagnose the problem, take your reader card with you. It could also be your reader card for the keyless go.
 

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Discussion Starter #5
The car battery was replaced few months ago.

Key battery changed (as indicated in original post), didn't help.

2005 no longer uses " reader card" (it's all in the key fob).

Anyway, I dropped it off at the MB dealer this morning (I'd rather avoid going to the dealer although the car is under warranty), we'll see ...

Thanks for your time.
 

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Hi lnguyenh

I have a cl500 2003. I was just wondering if you ever found out from the dealer what was wrong with your keys and why they couldn't lock or unlock the car doors and what they said the problem was, and how much it cost you to repair it and where? I'm having the same problem.
 

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Discussion Starter #7 (Edited)
Yeah it was finally fixed but I am afraid the answer will not be clear to you.

Dealer told me they replaced the battery on the fob. (and you don't want to know how much the "made in China" battery cost at the dealer by the way).

I worked while I was there at the dealer. When I went home, it stopped working again. I was a bit busy to bring it back so I left it there for few days. Afterward, it started working on and off for like two weeks and all of the sudden the problem went away after a couple of months.

I know this is not what you want to hear but I had no clue why it would fix itself. Also, your MY2003 doesn't have the keyless-go intergrated into the key fob like mine (yours still have a "card") so I don't know if it works the same.
 

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i'd bet there's a weak soldering connection somewhere on the electronics board of the key...they get dropped...they get thrown around...it's probably the most thrown around electrical piece of equipment on the car

the dealer usually suggest to order a 2nd key in this scenario to eliminate whether it's the key or the car
 

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Discussion Starter #9
I had two keys. One of them was almost never used (kept as a spare so it was virtually new). Both key gave same issues at the the same time and started working at around the same. I think it must be something else. Whatever it was, hope it won't come back :D
 
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