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Car doesnt read key FOB until the FOB is 1 foot away or less

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Car doesnt read key FOB until the FOB is 1 foot away or less

 
Old 02-22-19, 10:32 AM
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louczar
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Default Car doesnt read key FOB until the FOB is 1 foot away or less

The 2015 CPO I bought my wife last year just started doing this in the last month or 2. It doesn't do it all the time. I have replaced the batteries in both FOB's. It does it with both FOB's. I will take it back to the dealer to be resolved (as its under warranty). I was curious if anyone else experienced this and what was the cause?
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Old 02-22-19, 10:45 AM
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Another key/phone near the transmitter?

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Old 02-22-19, 11:08 AM
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How old is the car battery? If it is the factory one, it could be fading away now. That can indeed shorten the range of a key fob.
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Old 02-23-19, 06:41 PM
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Default Change the key fob battery

Sounds like you need to replace the key fob battery. Why don't you give that a try before you replace your car battery?


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Old 02-24-19, 04:48 AM
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He has already replaced the key fob batteries. Read the initial post.
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Old 02-24-19, 04:58 AM
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If I have my phone (especially with WiFi turned on) and key fob in the same pocket.......the key fob does not work at all!!!

Originally Posted by salimshah View Post
Another key/phone near the transmitter?

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Old 02-25-19, 05:40 AM
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Thank you for the replies. I am willing to bet that the car battery is still the OEM. I will take a look tonight and measure the voltage of when when off.
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Old 02-25-19, 06:59 AM
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When you replaced the key fob batteries, did you clean and burnish the battery contacts inside the key fobs? That could make a difference. If your car battery still tests more than 12.7 volts while sitting unused, I would clean and burnish those fob battery contacts as a next step.
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Old 02-26-19, 12:14 PM
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If the car starts fine than it's not the car battery.
If both key fobs do it, but then sometimes both key fobs work fine like you mentioned, that means it's not the key fobs.
I suspect its the key fob sensor, so do go to the dealer.
You did not specify what is not working, is it unlocking the door or starting the car?
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Old 02-27-19, 04:42 AM
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Failing batteries often have enough juice left to start the engine. The problem ensues when they then have to run all the electronics. Keep in mind that vehicles these days are essentially rolling computers.

As I mentioned before, your battery needs to measure at least 12.7 volts prior to start-up before it can be considered "good".
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Old 02-27-19, 07:37 AM
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Originally Posted by RX in NC View Post
Failing batteries often have enough juice left to start the engine. The problem ensues when they then have to run all the electronics. Keep in mind that vehicles these days are essentially rolling computers.
I must disagree.
Yes, the car has dozens of computers on board, but computers run on 5 volts, not 12. They use voltage regulators to regulate voltage.
Plus, all the computers may pull a few amps, maybe 10, but the starter may pull 100 or 200 amps.
Also, the OP has a problem with the key fob. The only time you may have a problem with the key fob is when the car is off, which means most of the computer units receive no power.
But all this does not help the OP resolve their problem, and replacing old car battery is always a good idea

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Old 02-27-19, 12:54 PM
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In the Jaguar world, one of the indicators of a dying battery is when the key fobs begin to suffer from diminished operating range. This is a well-known fact on the Jaguar forum that I have been a member of for more than ten years now. I experienced this issue myself with both my now-sold 2005 S-Type sedan and my wife's current 2006 XK8 convertible. Whether this anomaly applies in the Lexus world, I do not know. But I mention this so the OP will know that it may indeed be a possibility.
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Old 02-27-19, 02:14 PM
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Originally Posted by Non View Post
I must disagree.
Yes, the car has dozens of computers on board, but computers run on 5 volts, not 12. They use voltage regulators to regulate voltage.
Plus, all the computers may pull a few amps, maybe 10, but the starter may pull 100 or 200 amps.
Also, the OP has a problem with the key fob. The only time you may have a problem with the key fob is when the car is off, which means most of the computer units receive no power.
But all this does not help the OP resolve their problem, and replacing old car battery is always a good idea
Almost everything in this post is wrong.
I am fairly certain the computers in the car run on 12V, and the sensors run on 5V reference voltage (O2 sensors, TPS, etc). The voltage regulator maintains voltage at the battery at the same level to your lights as to your computers. The voltage regulator can only prevent HIGH voltage by "shutting off" the alternator. It cannot prevent your voltage going low except by very limited means (shutting off interior courtesy lights, for example).

Amps don't matter in this case. The computer might pull only 10A but if you turn on all the seat heaters, roll down all the windows, and start the car all at once, it will still pull down the voltage since the system is asking for more amps than a bad battery can provide before the alternator kicks in. Again, the voltage regulator will not prevent a low voltage condition, which can affect warning lights.

If your computer does not receive power when the car is off, how do you expect the car to recognize the key, illuminate the courtesy lamps, and unlock the car when you approach? The computer does get power with key off engine off.
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Old 02-28-19, 07:15 AM
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Originally Posted by N4TECguy View Post
Almost everything in this post is wrong.
I am fairly certain the computers in the car run on 12V, and the sensors run on 5V reference voltage (O2 sensors, TPS, etc). The voltage regulator maintains voltage at the battery at the same level to your lights as to your computers. The voltage regulator can only prevent HIGH voltage by "shutting off" the alternator. It cannot prevent your voltage going low except by very limited means (shutting off interior courtesy lights, for example).

Amps don't matter in this case. The computer might pull only 10A but if you turn on all the seat heaters, roll down all the windows, and start the car all at once, it will still pull down the voltage since the system is asking for more amps than a bad battery can provide before the alternator kicks in. Again, the voltage regulator will not prevent a low voltage condition, which can affect warning lights.

If your computer does not receive power when the car is off, how do you expect the car to recognize the key, illuminate the courtesy lamps, and unlock the car when you approach? The computer does get power with key off engine off.
Not wrong but misunderstood, sorry but English is my second language.
First, there are multiple separate computer units on the car, there are dozens of computers governing different parts.
And yes, all the computers receive 12 volt power, and the voltage regulator I mentioned id inside each computer box, it converts 12 volts to 5 volts, because TTL transistors run on 5 volts.
And last, I think I said that when the car is off, most of the computers are off, not that all are off. Because the computer that runs the lack/unlock function and the lights (headlight too) is obviously working, ready and waiting. But the computer running the fuel injectors, the TMPS system, the stability control, the ABS breaks and all the other computers that are only used to run the engine are off and not receiving power until you push the start button.

My point was that I don't believe that the car battery could fail in a way that there would not be enough power for the lock/unlock computer, but still enough power to turn the V6 engine over and start.
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Old 02-28-19, 07:33 AM
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But I wanted to add that I'm ready to change my mind when the OP comes back and tells us that he replaced the car battery and now the problem is fixed, I will learn something new
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