I recently went to dinner and let the valet park my 2006 SL65. Well, unknown to me, the valet guy turned the headlights from "auto" to "on". So when I got home, my headlights stayed on overnight until the battery died. Since the car has two batteries, the car was able to start the next day, but BOTH keyless go keys no longer work. They will both unlock and lock the car remotely, but only if you point the key at the car. The message "key not detected" pops up on the display if you try to use the keyless go feature to start the car. I put new batteries in the key fobs, but it did not fix the issue...... I drove the car around for 30 minutes with the key in the ignition, so that the convenience battery would charge, but that did not fix the issue either.

Now what do I need to do? Take it to the dealer?

Charge the rear battery

The rear battery is the convenience/consumer one. Once the "consumers offline" message disappears it should be charged enough...

Perhaps a longer drive/charge might fix it, worth a try. But if not the dealer might have to do some magic.

I charged the rear battery. No help, keyless go still not working. It's like the radio wave antenna for the key fob does not work, only the infrared sensor on the door.

xGot my car back from detroit motorwerks after it sat there for 3 months. Consumer batt was dead and would not accept a charge. Benz came out n replaced under warranty but still no keyless?? Same story as yours. Took it to my tech and he tried unsuccessfully to re-initiate both keys. My next stop will have to be the dealer unless someone has a solution to give us.

When I took delivery of my SL63 last month, after the test drive, I got the message "consumer offline", so all electronic consumers were off, including keyless go. The reason of the low of the rear battery was most probably because the car has been sitting on the dealer lot for extended time. The sales manager proceed to exchange the rear battery with another rear battery from a just delivered SL550. After the install of the newer battery the tech actually has to go thru somekind of set procedures with his MB computer on my car. I wonder whether going completely flat on the rear battery necessitates going thru this procedure (at the dealer)??

HTH,

Any update on what the cause of the "key not detected?" I have the same issue.

I recall reading that if you disconnect/mess with the rear battery with the keyless go fob near it...something (bad) happens. I put a little sticky note on the rear battery terminals that say get the key fob well away from the car before touching the rear battery.
Sorry I cannot be more specific but maybe this will job the experts into a real answer.

I had a problem with a loss of keyless go recognition (when my 2003 sl was still using keyless go cards) . If I set the card next to the shifter and drove around .... it would re-recognize it (in less than a day) . This worked several times for me when the card went unrecognized. It seems likely you might have the same result with your key

hope that helps,
Chris

Could be your key battery?

I have had an issue with just the keyless go button not working. MB found that the connection had debris(?) that was causing a contact issue - they didn't tell me any further details. The shifter button contact connection was cleaned and the problem resolved.

Depends on what year your SL55 is. The early models had a card (2003 - maybe 2004?) but the later cars with keyless go do not have a card. If you are getting a "card" message, it appears that you have a early car.