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Keyfob Distance So The Car Sensor Doesn’t Suck Power

5K views 34 replies 14 participants last post by  ChallyTatum 
#1 ·
I keep getting low keyfob battery alerts from EVIC. Today I got the “keyfob not detected” and my car wouldn’t start. I read a bunch of old threads that there was a known problem. Some said the car will continuously suck power from the fob if stored too close. Thing is, I don’t know what the minimum distance is so this doesn’t happen. I replaced the batteries and check the voltage and sure enough in both fobs they were below 3 V. Now they’re both reading 3.25 or so After replacing the batteries. Can anybody chime in on that distance? Thanks guys

P.S., I realize I can pop off the start button and manually start it but it’s still a nuisance.
 
#2 ·
once you're ~ 8' away and greater you're out of the range of the antennas (there's several on the car) to detect the fob.

then the CANBUS will go to sleep mode and not communicate with the fob
 
#16 ·
If they are in Faraday pouches, they can be touching the door handle and the car won't see them (know from personal experience). Even with the top velcro open my car didn't see them until I slid the fobs to the opening ;)

A Guy
 
#17 ·
I thought you had to touch the door handle which then sent out a coded signal that activated the fob. The fob then sent a coded signal back to the car. That's supposedly how the relay attack theft system works. One thief has to touch the door handle while his partner stands next to the house, hopefully with the fob close by inside. IOW neither the car nor the fob continuously sends a signal. That's my understanding.anyway.
 
#20 ·
I just put my 2014 Challenger and 2017 Grand Cherokee key fobs in a metal cookie tin in my kitchen, not far from the inside garage door. Never had a problem. In fact, you can carry the whole tin up to the car and grab the door handle and nothing happehs. Take the lid off the tin and everything works. Also, FWIW I don't lock either vehicle while in my garage.
 
#21 ·
I lock mine in my grandmas garage....trust no one!

-Dogg
 
#25 ·
I wonder if the fob boards have some residual flux or some other contaminant that is causing a current drain? I have read lots of post with guys having fob issues with pre-2015 challengers which makes me also wonder if the system is buggy to begin with? I think in 2010 or 2011? there was a recall or TSB for the WIN module replace. I would start with checking and cleaning the boards first and then make sure the replacement batteries are fresh. If the faraday bag isn't helping then it has to be something related to the fob board.

On a side note I also have a 2013 cherokee and it sits a little further away from the keys when parked in the garage and I only had to replace their batteries twice (the JGC gets used far more than the 2015 challenger).
 
#26 ·
My batteries lasted 3 years and the car never gave me any warnings. I've had 2 instances of the FOB refusing to send lock/unlock, remote start, or open trunk signals, but I could drive the car with the keys in my pocket and without issue.

Since the dealer refused to diagnose this at all and just told me to replace the batteries, I have no clue if it's the FOB failing or something within the car going haywire.

If it matters, I was keeping my car locked every night, has not happened since I moved and I no longer keep the car locked.
 
#27 ·
I have the “Passive Entry” system disabled via the Uconnect screen. Touching the door handle will not send a coded signal to the fob to activate it. I have to push a fob button to unlock the door but no big deal since I need a free hand to open the door anyway. I did this to prevent the car being stolen by thieves using the relay attack method.
 
#32 ·
2016 it's Settings> Door and Locks

A Guy
 
#34 ·
I replace the FOB battery yearly as "normal" maintenance.
 
#35 · (Edited)
Here is some more info on the distance in which the FOB actively communicates with the car.

"The Passive Entry (PE) antenna units (there are a total of 5 antennas) allow the transmitter within the Radio Frequency Hub (also known as the RF Hub) to communicate via Low Frequency (LF) radio transmission with a FOB with Integrated Key (FOBIK) that is located inside the vehicle or, at most, about 2 meters (6.5 feet) horizontally in all directions around the outside of the vehicle. The RF Hub uses communication through the antenna units to wake up and challenge a FOBIK that is within range in order to authenticate whether that FOBIK is valid (programmed) to the vehicle. The RF Hub communication with the FOBIK is on 20 kilohertz using Frequency-Shift Keying (FSK) modulation."
 
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