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Thread: Shouldn't low FOB battery show up on Dash?

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    Shouldn't low FOB battery show up on Dash?

    For the last 4 days when I went to start the car in the morning, nothing, no green, orange, red on the start button. When I take the FOB and wave it around close to the start button it will eventually turn green and start.
    The rest of the day it works fine, even when it's in my pocket.

    I thought I would get a low battery warning on the dash if indeed the battery is low.
    Don't have access to the other FOB right now but will check it when my wife returns from out of town.

    Wonder if these FOB batteries sit around or if the dealer refreshes them when you take delivery of the vehicle.

  2. #2
    Structural Member shadonoz's Avatar
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    Quote Originally Posted by wlong01 View Post
    For the last 4 days when I went to start the car in the morning, nothing, no green, orange, red on the start button. When I take the FOB and wave it around close to the start button it will eventually turn green and start.
    The rest of the day it works fine, even when it's in my pocket.

    I thought I would get a low battery warning on the dash if indeed the battery is low.
    Don't have access to the other FOB right now but will check it when my wife returns from out of town.

    Wonder if these FOB batteries sit around or if the dealer refreshes them when you take delivery of the vehicle.
    You should. I've gotten the warning on both of my original batteries. One after about 18 months, the next after about 6 month [2 years after delivery]. The warning came before any malfunctions.
    They're standard cr2025s. They can't be recharged, and I'm sure the dealer doesn't replace them when new.
    Since you have a 19, it seems too soon for the battery to fail, but always check that first!

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    The thing that makes no sense to me is the Key Warning Indicator is supposed to be white if the FOB battery is dead. But how would it even know the FOB is in the car if the battery in it is dead?

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    Registered Member 7eregrine's Avatar

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    You get in the car with fob. You press button. Car looks for fob. Car detects faint signal. This is why it will work if you press it close to the button. It will never get to UTTERLY DEAD status unless you ignore it for weeks.

    Totally my theory, no facts included here.

    @OP: I've had this exact thing happen. It is probably just in a bad spot and didn't get the good detection on the signal. I think the car just didn't get a good 'look' at the key and assumes the battery is dead. Subsequent starts it 'sees' the key better.
    Last edited by 7eregrine; 10-08-2019 at 03:29 PM.

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    How long does it take a new fob to drain to 0%?

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    Quote Originally Posted by 7eregrine View Post
    You get in the car with fob. You press button. Car looks for fob. Car detects faint signal. This is why it will work if you press it close to the button. It will never get to UTTERLY DEAD status unless you ignore it for weeks.

    Totally my theory, no facts included here.

    @OP: I've had this exact thing happen. It is probably just in a bad spot and didn't get the good detection on the signal. I think the car just didn't get a good 'look' at the key and assumes the battery is dead. Subsequent starts it 'sees' the key better.
    So in theory, I should be able to get into the car with no FOB on me, press the button, and the FOB Battery indicator should say Dead Battery.

    I'll have to give it a try.

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    Quote Originally Posted by mutualcore View Post
    How long does it take a new fob to drain to 0%?
    It would likely depend on how often you push the buttons on it.

    I have my doors automatically "Walk Away Lock," so I never use the FOB's transmitter to lock/unlock them or to open the hatch. My battery is likely to last the longest under those conditions.

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    Quote Originally Posted by Avoidin Deer View Post
    So in theory, I should be able to get into the car with no FOB on me, press the button, and the FOB Battery indicator should say Dead Battery.

    I'll have to give it a try.
    I think you'd get a "Key Not Detected" error. The car needs to be able to detect the key in order to determine if the battery is low.
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    Structural Member shadonoz's Avatar
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    Quote Originally Posted by Avoidin Deer View Post
    So in theory, I should be able to get into the car with no FOB on me, press the button, and the FOB Battery indicator should say Dead Battery.

    I'll have to give it a try.
    Quote Originally Posted by sm1ke View Post
    I think you'd get a "Key Not Detected" error. The car needs to be able to detect the key in order to determine if the battery is low.
    Mine first says "key not detected" and then "low battery".

    So it does NOT need to detect the key. If it doesn't detect it, it assumes the battery might be low.

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    Quote Originally Posted by 7eregrine View Post
    You get in the car with fob. You press button. Car looks for fob. Car detects faint signal. This is why it will work if you press it close to the button. It will never get to UTTERLY DEAD status unless you ignore it for weeks.

    Totally my theory, no facts included here.

    @OP: I've had this exact thing happen. It is probably just in a bad spot and didn't get the good detection on the signal. I think the car just didn't get a good 'look' at the key and assumes the battery is dead. Subsequent starts it 'sees' the key better.
    I don't know if I can buy the bad spot. I've had my 16 for 4 yrs and wear the same type of pants/shorts and it has never missed. Plus on the 19 it detects the FOB since it lets me unlock the drivers door with the FOB in my pants pocket. I will change the battery when I'm able to and go from there

    It's weird because I went out this morning and had trouble. Went out two times after that later and no problem. Same pants, FOB in same pocket.

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    Change your battery and see if that fixes it.

    If not, use the other fob for a while and start to narrow down the problem point.

    ps: Apologies for using upper case letters for fob. It's a noun, not an acronym for Free On Board. Five years into retirement and I just can't break the habit.

  13. #13
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    My first FOB battery lasted 3 years. I probably prematurely replaced it again a couple years after when I thought it was dead again, but ended up being a switch under the gated shifted in my 2014.
    2014 CX-5 Touring AWD 2.5L | Jet Black Mica - 86k miles
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    Quote Originally Posted by sm1ke View Post
    I think you'd get a "Key Not Detected" error. The car needs to be able to detect the key in order to determine if the battery is low.
    But there's a "Battery Dead" warning. Is there a way to detect the key if its battery is dead? (Honest question, there's RFID technology that does not require a power source.) There's got to be a way to know there's a key present to tell you that its battery is dead.

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    Structural Member shadonoz's Avatar
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    Quote Originally Posted by Avoidin Deer View Post
    But there's a "Battery Dead" warning. Is there a way to detect the key if its battery is dead? (Honest question, there's RFID technology that does not require a power source.) There's got to be a way to know there's a key present to tell you that its battery is dead.
    Guess you didn't see this, or didn't understand the implications.

    Quote Originally Posted by shadonoz View Post
    Mine first says "key not detected" and then "low battery".

    So it does NOT need to detect the key. If it doesn't detect it, it assumes the battery might be low.
    It gives the low battery warning when the battery reaches a voltage threshold, long before it ever goes dead.

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