ddskier

I own a 2007 E550 with Keyless Go. For the past 3 weeks I have been having intermittent Keyless Go issues where the car will not recognize the key. Naturally when I hit the lock/unlock buttons or start the car manually it works fine, but the damn keyless system will just pop-up “Key Not Recognized”.

Steps I have followed to fix the issue before taking it to the dealer :

1. Replaced the batteries within the key itself.
2. Switched to the secondary key provided with the car.
3. Made sure not to leave it in the car overnight. (My dad drained his key battery by doing that.)


I have taken the car to the dealer, but of course that day it worked just fine and they couldn’t reproduce the problem. Naturally it’s happened again since then….


Does anyone have any ideas on what to do with this?

Dogshine

where is your key when it isn't working? when mine is in my pocket behind my cellphone sometimes it won't work.

Barry45RPM

I had that exact same issue with my '04. If you ARE stepping in the brake pedal hard enough while pressing start, it is a bad stop light switch. Once they changed the switch, it neve happened again. Suggest this to them. Sometimes my car would stop in mid crank & flash "key not recognized".

It will always start with the key in the ignition, even when it won't with the keyless.

cyclerider

The one time my wife's key wasn't recognized it was in her purse with her cell phone laying right on top of it. Moving the cell phone immediately cured the problem.

Page 111 of the owners manual states: "Never store the SmartKey with KEYLESS-GO together with electronic items such as a cellular phone . . ."

ddskier

Thanks for the info on the cellphone. I normally keep the key in my pocket which is right below my cellphone attached at my belt. I'll see if that is what is causing the problem.

FYI - I also receive the same issue trying to unlock / lock the door so it isn't a break pedal issue. (Nice idea though.)

youngbd

I have had the same problem and I can understand the brake switch. This is something I will look into. But I also noticed that not only does KEYLESS GO not work, but also the doors and trunk will not open because the "key is not recognized". What I have noticed, being in Michigan, is that it appears to be temperature related. When the temperature is over 38 or 40 degrees F, I have never had this problem. But when the temperature drops below that I always have this problem. Any ideas?

Thanks!
B Young.

konigstiger

I believe the manual instructs not to keep the KG key together with electronic equipment, such as a mobile phone, or metallic objects, such as coins or foils.

How KG functions…

Unlock request:
- With key present, switch on inside of driver’s door is activated
- Door handle switch is connected to the rear door KG control module
- Rear door KG control module communicates request to EIS
- EIS transmits command signal to left rear door KG control module
- Left rear door KG control module uses antenna to send a RF signal to wake up the KG key
- Key within range wakes up
- Key transmits authorization code via RF
- RF signal is received by rear window antenna (connected to right antenna amplifier module)
- Right antenna amplifier module send signal to rear KG module
- Rear KG module sends key data to EIS
- EIS provides KG authorization
- EIS generates an “unlock” command plus a signal to left rear door KG control module to open driver’s door when handle is pulled

Interior Compartment Module (located behind ashtray) antenna confirms that key is inside vehicle.

The KG key includes a chip card function and the LED flashes when key responds to a wake-up request.

The Brake Switch signal is required when starting the engine.

The unlock/lock key buttons use IR (infrared) signal whereas KG uses RF (radio).

Benz-O-Rama

I have an intermittant problem where I walk up to the car and pull the door handle but it doesn't open. I'll wait a couple of seconds and try it again. Sometimes it works on the second try sometimes the 3rd or 4th and sometimes not at all and I have to push the unlock button on the key.

Key battery perhaps? Oh and the key is in a pocket all by it's lonesome.

Konigs...

You say "RF signal is received by rear window antenna (connected to right antenna amplifier module)"

Could window tint cause a problem? I also have very poor FM reception that the dealer is blaming on my window tint.

konigstiger

When inoperable, take note if the key responds to the wake-up request (i.e.: key LED flashes). The key battery can be checked by pressing the lock or unlock button. If the LED under the panic button comes on the battery should be fine. If the tint is non-metallic it shouldn’t make a difference. However, check to see if any of the wiring on the rear window (upper area) was damaged during install. This may also be the reason for poor FM reception.

MB Fanatic

Certain window tints can interfere. Do you have Ceramic window tint?

Metallic window tints, the most popular, can cause such issues with Keyless Go, Navigation, etc.

AMGFREAK

Had this problem also in my E320 CDI. You need to use your key to start your car every so often to keep the car and key in sync. Just what my dealer told me. I have not had any problems since. Hope that this helps.

ddskier

FYI - I switched to carring my key in my other pants pocket, away from my cellphone. Since then I have not been able to reproduce my "Key Not Recogonized" issue.

This change seems to have fixed it for me.

Also please be aware that my dad with his S600 was told not to keep his "keyless go" key in the car overnight. Apparently this tends to drain the key's battery at a much higher rate than normal.

MB Fanatic

Yes, leaving the key in, or near the car all the time will drain the battery. The car is keeping the key "alive" so of course its going to drain it. This can be traced back to Konigstigers, post above.

Talbot

I have a semi-related question... If two people get into the car with keys, can the car detect which is the driver to enable that driver's settings?

Barry45RPM

The manual states not to have 2 keys in the car... I don't know how this isn't possible if say the husband and the wife both have keys to the car because the wife occaisionally drives it, yet when they enter the car together the 2 keys are in the car at the same time.

I'm pretty sure that the car recognizes one of the keys as key # 1 and the other as # 2, and that if both are in the car, the car will obey key # 1's pre-sets, unless the car is not set to "key dependent" on.