Keyless Go Push Button Start Problems
 

Recently (last 6 months) the Push button start in our 2014 E250 has intermittently failed to start. The starter makes a sound and effort to start, but stops. Usually happens first attempt during the day. I pop it out with my fingers and start the car with the key. After that, the push button start usually works normally. I think it might have something to do with humidity or temperature, but I can't tell. The car is garage kept at night and during the day. All normal MB maintenance has been completed as per MB schedule.

Any ideas or advice?
Thanks in advance

If you haven't already, I would first check the charge in the remote battery, or just install a fresh battery. Then, remove the button and blow out the ignition socket with Computer Air, and then thoroughly wipe/clean the business end of the button to be sure it isn't dirty.

My older MB worked via IR sensing of the key in the ignition. That key had an obvious round window in the key, and a corresponding window in the ignition. The newer keys don't have the round window, so if IR is used to read the key (or the button) it isn't obvious. Bottomline, cleanliness of the contacting parts may clear up the problem.

There isn't much else you can do from the outside. If that doesn't clear up the intermittent failure, then I would suspect something within the switch itself. Let's hope it isn't that.

Yeah, when did you last change the fob key battery? Most get 6 months to a year of life. I get about a year out of a fresh battery. If you store your key too close to the car they may try to communicate when you aren't around and wear down the fob battery. I have had issues in the past of my key and proximity to my iPhone causing issues, so I never keep them together any longer and the start problem or key recognition issue has not returned. These cars can also be started with a completely dead fob battery, so keep that in mind if you have a more serious issue and the fob does not open your door. Use the blade key to get in and remove the push-to-start button and insert your key to start. It will start the car with a completely drained fob battery.

I was wondering something similar. What happens if you press the button a second time?

The car will start with the key in the ignition, because the key uses a different (failsafe) system to start the car, as I described above. If the car wakes up (position 1) when you push the button -- but does not start -- with the key in your pocket, it most likely is because something is amiss with the wireless recognition of the key. Pressing the button a second time will not help the system recognize a key it did not recognize on the first try.

Checking the battery is the first step, and a very simple one, too. Please let us know what develops.

No, just not true. The thing that causes communication between car and key is something physically touching the car, like your hand on the door handle, or pressing the start button, and the car THEN needs to see where the key is. The car doesn't just randomly search for the key, thus depleting the key battery.

I don't think this is true, either...

In reading several threads here, I believe the key transmits a signal anytime it is moving. If it sits still on a countertop for several minutes, it turns off to conserve the battery. On the other end, the car is awake at all times and scanning for a valid key to walk into range. As you walk to the car, the key (now in motion, awake and broadcasting) is sensed by the car which is now ready to respond. One need not touch the car, as evidenced by the motion sensor activated trunk opener (no touch necessary to open the trunk, even when the car is locked). No touch necessary to unlock the doors from afar, either.

What is not clear to me... If you leave the key in the car at rest (engine off), will the battery drain until the key (also at rest) times out? Or will it stay on as long as it is actively linked to the car?. That will really drain the key battery.

Either way, it's recommended not to store the key anywhere near the car, so don't leave it in the ashtray when you park it in the garage and walk inside. Take the key inside with you (out of car range) and sit it someplace where it will eventually turn itself off.

wrongo. Where did you get this info? The car does search for the key as it enters its proximity. That distance varies depending on various factors and the car will wake up.

How would the car know if the key was entering proximity? And why would the car do that? Does it do that 1 time every minute? every 10 seconds? Every second? If it did, surely your battery wouldn't last even a month. What happens when the car wakes up? What does the car do?

Either you do something with the key fob or you do something at the car, but they don't just talk to each other to see where the fob is without specific input. Think about what you said. It does not make sense to build a system into a car in that manner.

So if you have your key fob in your pocket and you walk around for weeks after your flight to New York while your car is in Los Angeles, your fob is transmitting just in case the car is nearby?? And the car is scanning all the time looking for a fob? Why would it do that? It doesn't make sense.

Sure, there is a sensor for the motion sensor for the trunk, similar to touching the car. You can't unlock the car from afar without a key fob in use, physically pressing the lock/or unlock button.

I keep my key near my car about 6 ft away ALL THE TIME. My fob battery lasts as long as yours does.

^ ok, then how can I swipe my foot under the car trunk and the trunk will open. I have not touched the car nor my key fob. Is that trunk sensor constantly powered up and active 24/7 or does the car sense the key in range by monitoring for a signal?

Please re-read my earlier post. Your car is semi-awake at all times. There is a small fan in the overhead console that blows air over a cabin air sensor. It works 24/x7x365xXX years. The anti-theft alarm system is awake 24/7, even when not armed. There are several other systems that work around the clock, not to mention your actual dashboard clock. All of these systems draw small bits of power.

The key sensor is one of them. The car wakes up to a higher state when its (active) sensor detects the presence of the signal from a valid key tied to the car.

If your car is parked in the garage when you are out of town for days, take your house key, but leave that bulky key fob in a drawer where it doesn't move and turns off. Then, only the car is semi-awake.

There are several posts here quoting dealer service techs cautioning that you should store your key out of car range to preserve its battery. Do a search.

and this is how thieves have been able to steal your car without the key. They grab the signal from the key in your home stored by your car (6' away for you, which is in your garage). that signal is transmitted to another device which is placed near the car. The car senses it, wakes up, the door opens and the bad guy drives away. There was a story on the news the other day that said to drop your keys into a tin can at home to thwart this active high tech burglary.

The car monitors the car trunk sensor, which is powered by a HUGE BATTERY in comparison to what is in your key fob. When it senses the movement, it then sends a signal to the fob to see if the fob is nearby, and if it is, message sent back to car and trunk opens. This is the same process as opening a door, except that there is no physical touch required for the trunk. For the door, the car monitors the door handles which are powered by a HUGE BATTERY in comparison to what is in your key fob. You touch the handle, car senses the touch, it then sends a signal to the fob to see if the fob is nearby, and if it is, message sent back to car and door opens opens.

Yes, when you use the key fob to open the door, the car responds because it is listening for the signal, or if you use the foot swipe, the car responds. Point is that they do NOT talk back and forth with each other wearing out the small key fob battery 24 hours a day. Action on the key fob, or touching the door, or foot under trunk signals the car to react. No constant conversation involved.

Sonnyslope48, page 91 of the owner's manual describes how to deactivate Keyless Go on the Smartkey...

"If you do not intend to use a key for an extended
period of time, you can deactivate the
KEYLESS-GO function of the SmartKey. The
SmartKey will then use very little power,
thereby conserving battery power. For the
purposes of activation/deactivation, the
vehicle must not be nearby."

The reason why the car must not be nearby has been explained to you several times now. If you are unable or unwilling to accept correct answers, then I (we) have nothing more for you.

back on topic...

stevil555, please let us know if you have tested the battery in your keyfob and whether replacing the battery has solved your issue.

That statement does NOT support your position. And it has nothing to do with the general operation of the keyless go system. Perhaps you have something from Mercedes which backs your position??

Regardless, just change the key fob battery. I usually have a small supply of them from eBay. They normally only last 3-4 months for me. Not sure if it's because of other keyless go keys that I have or I just change them whenever I get a battery low message. When they're new, battery voltage is in the 3.24-3.26 range, when the battery low message pops up, they're down to about 3.06. I did let it go once for a little while and the message stopped popping up after a while. When the key battery in the fob is dead, it won't start the car and you have to use the rfid chip in the key to start the car which doesn't require any power.

Change the battery and report back. Make sure you use fresh ones, sometimes the ones in the local stores like CVS, Target are old and half dead.

Sorry, was out of town. I will check on these things and report back. Thanks for all of the advice!

"The system works by having a series of LF (low frequency 125 kHz) transmitting antennas both inside and outside the vehicle. The external antennas are located in the door handles. When the vehicle is triggered, either by pulling the handle or touching the handle, an LF signal is transmitted from the antennas to the key. The key becomes activated if it is sufficiently close and it transmits its ID back to the vehicle via RF (Radio frequency >300 MHz) to a receiver located in the vehicle. If the key has the correct ID, the PASE module unlocks the vehicle. "

The complete text is available here:https://en.wikipedia.org/wiki/Smart_key

I changed the battery in both fobs and there was no change in the behavior.

Thanks for all of the ideas. I guess to the dealer I must go.

I am sure it is the same for everybody else but when the battery is low in my key fob there is a warning on the dashboard to that effect.
The warning came on about 6 weeks ago, I haven't replaced the battery in the key fob yet, I want to see how long it will work before it dies (I keep a replacement battery in the glove box for that eventuality).
I don't know how old the battery in the key fob is as I bought the car used about a year and a half ago and haven't changed the battery yet.
It has certainly lasted more than a year.