Double check the polarity of the battery and/or check for bad solder connections on circuit board.
Key Fob Won't Work Even After Battery Replacement - Anybody Experience This?
I have 2 key fobs for my 2008 Smart... Key fob 1 stopped working for a few months now so I've been using key fob 2. About 2 weeks ago, key fob 2 stopped working as well so I bought some fresh batteries to put into the key fobs..
I put in the fresh batteries. However, key fob 2's transmitter functions (lock/unlock/panic/trunk) don't work at all... Key fob 1 works..
Has anybody experienced this weird phenomenon? Water wasn't spilled on the fob or dropped either...
Is there some kind of "reset" that I need to do to sync the key fob back up?
Thanks.
I put in the fresh batteries. However, key fob 2's transmitter functions (lock/unlock/panic/trunk) don't work at all... Key fob 1 works..
Has anybody experienced this weird phenomenon? Water wasn't spilled on the fob or dropped either...
Is there some kind of "reset" that I need to do to sync the key fob back up?
Thanks.
1 - 20 of 32 Posts
Thanks for the reply.Double check the polarity of the battery and/or check for bad solder connections on circuit board.
I double checked the polarity of the battery by comparing it to the working key fob. I also swapped out the battery between the two key fobs but no luck.
The solder joints seem to be fine as well. The part that has tensioned prongs seem to be well connected and the other terminal is just connected to a gold block in the PCB.
Seems like I remember this being a common issue. This happened to me on my 2010, ended up replacing the battery and still no response. I switched to my second key fob and never looked back.
Resurrecting this thread with the same issue on a 2012. Has anyone figured out an answer? I just bought a 2012, one fob is working fine, the other one's housing was broken and the remote buttons were not working. I changed the battery but still not working. That key/fob does work in the car though, opening the door manually and starting the car. I will examine the circuit board for any broken solder joints, but has anyone else run across this issue?
Tried cleaning the areas on the circuit board where the inner “buttons” make contact? Got them lined up?
I bought a 2011 and it came with 3 remotes. However only 1 remote would lock and unlock the car. 2 remotes would start the car and it bothered me why the remote would start the car, but not lock or unlock it. Several months went buy and I bought a dedicated Mercedes scanner to clear my ABS code from changing the seat.
As I scanned through all the codes on the scanner I noticed a code for remote stating, "battery inserted wrong polarity". I didn't think much of it and cleared it anyway. I then correctly inserted the CR3032 battery into the remote, and tested it, and guess what, it works, I now have 2 remotes which start and lock/unlock the car.
now what I am thinking is that if you by some chance inserted the battery in the wrong position, thus reversing polarity, it registers this on the computer and logs it as an error code, requiring it to be cleared before authorizing it to lock and unlock the car, however it still allows you to start the car.
The scanner was from amazon.com for $150 US funds
iCarsoft MBII for Mercedes Benz/Sprinter/Smart Professional Diagnostic Tool Scanner, New Version
As I scanned through all the codes on the scanner I noticed a code for remote stating, "battery inserted wrong polarity". I didn't think much of it and cleared it anyway. I then correctly inserted the CR3032 battery into the remote, and tested it, and guess what, it works, I now have 2 remotes which start and lock/unlock the car.
now what I am thinking is that if you by some chance inserted the battery in the wrong position, thus reversing polarity, it registers this on the computer and logs it as an error code, requiring it to be cleared before authorizing it to lock and unlock the car, however it still allows you to start the car.
The scanner was from amazon.com for $150 US funds
iCarsoft MBII for Mercedes Benz/Sprinter/Smart Professional Diagnostic Tool Scanner, New Version
Interesting! Does that tool do the proprietary fault codes and live data such as the transmission codes? Does it allow "coding" modules for doing things like adding power steering?I bought a 2011 and it came with 3 remotes. However only 1 remote would lock and unlock the car. 2 remotes would start the car and it bothered me why the remote would start the car, but not lock or unlock it. Several months went buy and I bought a dedicated Mercedes scanner to clear my ABS code from changing the seat.
As I scanned through all the codes on the scanner I noticed a code for remote stating, "battery inserted wrong polarity". I didn't think much of it and cleared it anyway. I then correctly inserted the CR3032 battery into the remote, and tested it, and guess what, it works, I now have 2 remotes which start and lock/unlock the car.
now what I am thinking is that if you by some chance inserted the battery in the wrong position, thus reversing polarity, it registers this on the computer and logs it as an error code, requiring it to be cleared before authorizing it to lock and unlock the car, however it still allows you to start the car.
The scanner was from amazon.com for $150 US funds
iCarsoft MBII for Mercedes Benz/Sprinter/Smart Professional Diagnostic Tool Scanner, New Version
LOL, I went to do this and realized that the "ground" tab for the battery was missing. I had ordered a replacement fob anyway due to this one being broken, put it all together with my original circuit board and key blade and it works perfectly. Thanks for the info!Tried cleaning the areas on the circuit board where the inner “buttons” make contact? Got them lined up?
I want to share how I got my Smart key working again. I have two keys and one of key fob suddenly stop working all together for no apparent reason. Mine is 2008 Smart (451). Thought it was dead battery so I replaced batteries many times but no response, nothing...It was working good and no worn cover or case etc. My other key works good so I even took out battery from good key and tried but the dead key still didn’t work. I then opened key fob and cleaned buttons and battery contacts with electric cleaner as well as raising battery contact pins so it gives better contact. This fixed and key now works great.
Sorry I'm late.
Came here for a solution then figured it out.
Pressed the lock and unlock buttons simultaneously and it started working.
Hope it helps.
Came here for a solution then figured it out.
Pressed the lock and unlock buttons simultaneously and it started working.
Hope it helps.
I have a key fob I never use. Tried it yesterday and it would not unlock. I put it in ignition, car started, and now the fob works again. I think it loses pairing with car if not used, and repairs when ignition is on. All good now 😅I have 2 key fobs for my 2008 Smart... Key fob 1 stopped working for a few months now so I've been using key fob 2. About 2 weeks ago, key fob 2 stopped working as well so I bought some fresh batteries to put into the key fobs..
I put in the fresh batteries. However, key fob 2's transmitter functions (lock/unlock/panic/trunk) don't work at all... Key fob 1 works..
Has anybody experienced this weird phenomenon? Water wasn't spilled on the fob or dropped either...
Is there some kind of "reset" that I need to do to sync the key fob back up?
Thanks.
I still have both my original key fobs (2009). I have the habit of rotating my fobs each time I drive the car. I have never had a pairing issue and have only replaced the batteries twice in 13 years.
1983, that is a great suggestion. Thank you! I’m going to start doing that.
The fob won’t lose contact with the car. if it’s not use. The only thing that happens. The battery inside eventually dies. Rotating doesn’t do anything either. Just less wear and tear, on the key pads. They don’t wear out not using them. They are not blue tooth. Remote keyless systems consist of a key fob transmitter and a receiver inside the vehicle. They most commonly used radios frequency of 315MHz in the the U.S.I have a key fob I never use. Tried it yesterday and it would not unlock. I put it in ignition, car started, and now the fob works again. I think it loses pairing with car if not used, and repairs when ignition is on. All good now 😅
They do lose contact with the car when you don't use them. My second keys (for every car) are locked up in a safe and basically never get used.
Like the person above, I've noticed that if you let a smart's key do nothing for long enough it'll lose contact with the car. It happens with both my 2008 and my 2012 and it doesn't matter how new the fob battery is.
I haven't been able to figure out when the cut off point is, because sometimes it's a year or two before I even touch the second key.
But the solution is still the same. I unlock the door manually, stick the key in the ignition, and the key gets reconnected.
Like the person above, I've noticed that if you let a smart's key do nothing for long enough it'll lose contact with the car. It happens with both my 2008 and my 2012 and it doesn't matter how new the fob battery is.
I haven't been able to figure out when the cut off point is, because sometimes it's a year or two before I even touch the second key.
But the solution is still the same. I unlock the door manually, stick the key in the ignition, and the key gets reconnected.
They don’t lose contact, if not used. They use radio frequencies. Not Bluetooth.
I’ve own some 40 new and used cars, over my life time. The spare fobs,
always still work.
I’ve own some 40 new and used cars, over my life time. The spare fobs,
always still work.
Ok, let's just forget about "losing contact."
If you let your key do nothing for an indeterminate amount of time -- let's say two, three, or four years -- the buttons may not do anything the next time you try it. And a new battery may not fix it.
Don't go to the dealer and don't call the mechanic. Just stick the key into the ignition and start the car. Why has this happened to multiple people in this very thread? I don't know, but that's a working fix.
If you let your key do nothing for an indeterminate amount of time -- let's say two, three, or four years -- the buttons may not do anything the next time you try it. And a new battery may not fix it.
Don't go to the dealer and don't call the mechanic. Just stick the key into the ignition and start the car. Why has this happened to multiple people in this very thread? I don't know, but that's a working fix.
Miss Mercedes,
That should be a stickie tip of it isn’t already. Great stuff!
That should be a stickie tip of it isn’t already. Great stuff!
Confirmed that the key gets forgotten with my own eyes and experience, this would be my second time. I barely use this second backup key and if its been a while this will happen even though I use the other key every day and never change either battery.
Yes, a dead battery could of caused this, but I tested the battery and changed it and the problem still doesn't work until you this "magical", unwritten procedure. This is only if the buttons don't do anything but the car starts fine with the key. And I am using the 2016 Smart 451 ED (electric Drive), but this should work for all 451 Here is what has worked for me both times including today:
1) CHANGE THE BATTERY TO A NEW ONE (cuz why deal with the hassle to save $4)
2) Verify nothing is broken inside the key fob as best as you can. (worst case take it to an auto parts place like autozone and they usually have that machine near the replacement battery that checks if your key fob is transmitting)
3) Lock the car by using the button on the other working key fob if you have one (this is just the way I do it not necessarily the "correct way".
4) Using the non working key fob unlock the door physically by turning the key lock on the door clockwise.
5) I pressed and released each key (unlock then lock then rear hatch)
I think I closed the door with me inside after this (I hope this wasn't important)
6) Placed key in ignition slot
7) I pressed and released each key (unlock then lock then rear hatch)
8) Turned Key once to ACC on
9) I pressed and released each key (unlock then lock then rear hatch)
10) Started car
11) I pressed and released each key (unlock then lock then rear hatch)
12) Turned off car and took key out of ignition
13) I pressed and released each key (unlock then lock then rear hatch). This time all buttons are magically working now.
Are most/some of these steps un-necessary? Yea probably. But I don't care because I now have 2 working keys again. Hope this works for others as well, good luck.
Yes, a dead battery could of caused this, but I tested the battery and changed it and the problem still doesn't work until you this "magical", unwritten procedure. This is only if the buttons don't do anything but the car starts fine with the key. And I am using the 2016 Smart 451 ED (electric Drive), but this should work for all 451 Here is what has worked for me both times including today:
1) CHANGE THE BATTERY TO A NEW ONE (cuz why deal with the hassle to save $4)
2) Verify nothing is broken inside the key fob as best as you can. (worst case take it to an auto parts place like autozone and they usually have that machine near the replacement battery that checks if your key fob is transmitting)
3) Lock the car by using the button on the other working key fob if you have one (this is just the way I do it not necessarily the "correct way".
4) Using the non working key fob unlock the door physically by turning the key lock on the door clockwise.
5) I pressed and released each key (unlock then lock then rear hatch)
I think I closed the door with me inside after this (I hope this wasn't important)
6) Placed key in ignition slot
7) I pressed and released each key (unlock then lock then rear hatch)
8) Turned Key once to ACC on
9) I pressed and released each key (unlock then lock then rear hatch)
10) Started car
11) I pressed and released each key (unlock then lock then rear hatch)
12) Turned off car and took key out of ignition
13) I pressed and released each key (unlock then lock then rear hatch). This time all buttons are magically working now.
Are most/some of these steps un-necessary? Yea probably. But I don't care because I now have 2 working keys again. Hope this works for others as well, good luck.
I just acquired my second SmartCar, love em. Dealer supplied two fobs. One worked, one did not. Used the above advice and presto, both fobs now act appropriately. Many thanks for the hack.I have a key fob I never use. Tried it yesterday and it would not unlock. I put it in ignition, car started, and now the fob works again. I think it loses pairing with car if not used, and repairs when ignition is on. All good now 😅
1 - 20 of 32 Posts
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