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2021 Crosstrek Limited, Magnetite Grey, 1.5" ADF lift, RRW RR2-V 15x7, Geolandar G015 235/70R15
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When,not if,when,the battery goes dead in your wife's fob,the same thing will happen as when she lost it.It can't communicate with car so the car won't start.If you use the TS508 to test her fob from time to time,you will know when it's getting weak and you can change the battery before she gets stranded again.
This shouldn't happen. All modern vehicle fobs with PBS have 2 different forms of communication with the vehicle both passive and active RFID. Active requires battery power in the fob to communicate with the vehicle from a distance to lock and unlock the doors, turn on the approach lights when you walk up etc. without removing the fab from purse/pocket. The fob also has passive RFID in it which does not require battery power but only works in about 4 inch proximity to a receiver. The active radio receiver can be located anywhere in the car but the passive receiver is located in the push button on the dash. You can hold a dead key fob right next to the push button while you push the button and the car should start up and operate normally.

An anecdotal story along these lines. My previous vehicle was a 19 Ram with PBS. People on the forum were having problems with PBS. Prox sensor worked find to open the door but when they would get in the truck to start it they would get a message that the key fob wasn't in the truck and they would have to use the passive RFID and touch the fob the to the button to start the truck. The radio receiver for the RFID is located on the back wall of the truck and people were replacing the brake light bulbs in the CHMSL with cheap LED bulbs off of amazon that were emitting radio frequencies that were jamming the receiver and since you have to have your foot on the brake to start the car as soon as you stepped on the break the connection from the fob to receiver was jammed and the truck didn't think the fob was in the cab. Replace the offending bulbs with better led's or put the incandescent bulbs back in and everything worked fine.
 

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I got it at O’Reilly auto parts online. I did a shopping search on Google and it came up as one of the cheapest prices. Then I found a coupon code that brought it down more - can’t remember but think it may have been a St Patrick’s Day sale.
Thank you. And maybe another stupid question, does the autel tool only work with autel sensors? Or would I be able to use that with any sensors in the same frequency and when swapping back to oem wheels/sensors?
 

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This shouldn't happen. All modern vehicle fobs with PBS have 2 different forms of communication with the vehicle both passive and active RFID. Active requires battery power in the fob to communicate with the vehicle from a distance to lock and unlock the doors, turn on the approach lights when you walk up etc. without removing the fab from purse/pocket. The fob also has passive RFID in it which does not require battery power but only works in about 4 inch proximity to a receiver. The active radio receiver can be located anywhere in the car but the passive receiver is located in the push button on the dash. You can hold a dead key fob right next to the push button while you push the button and the car should start up and operate normally.

An anecdotal story along these lines. My previous vehicle was a 19 Ram with PBS. People on the forum were having problems with PBS. Prox sensor worked find to open the door but when they would get in the truck to start it they would get a message that the key fob wasn't in the truck and they would have to use the passive RFID and touch the fob the to the button to start the truck. The radio receiver for the RFID is located on the back wall of the truck and people were replacing the brake light bulbs in the CHMSL with cheap LED bulbs off of amazon that were emitting radio frequencies that were jamming the receiver and since you have to have your foot on the brake to start the car as soon as you stepped on the break the connection from the fob to receiver was jammed and the truck didn't think the fob was in the cab. Replace the offending bulbs with better led's or put the incandescent bulbs back in and everything worked fine.
Your idea of what "shouldn't" happen and what does happen are two different things.You obviously have no idea how the system works.There are two different transmitters but a receiver is a receiver.Any and all receivers will listen for a signal at all times so that when the signal it's been waiting for IS transmitted,it will be ready to do what it must do.Then,there's the two transmitters.There's the active transmitter that transmits a constant signal for the keyless features such as the door locks and push button start.Then,there is the passive transmitter which is activated by pushing a button on the fob for remote start,door locks or to sound the alarm.It uses an RFID signal.That's Radio Frequency Identification.The key word is "Radio".The fob must transmit a signal over a "radio" frequency to be received by the car.It's impossible to produce a radio signal over any frequency without electricity.If the battery is dead,you have no electricity,no radio signals are produced and thus the car doesn't start as has happened to many people.If there is enough power in the battery to produce a signal and the fob is held close enough to the receiver to pick up that weakened signal then yes,it will start.

As for your Ram,I'm sorry that Dodge/Fiat cheaped out on their electronics and didn't properly shield them from interference.However,there is no 2nd receiver.The farther away the fob is from the receiver,the weaker the signal will be when it reaches the receiver.If there is a source of interference,such as your LED's and the fob is far enough away from the receiver,the strength of the interference will drown out/jam the signal from the fob and the car won't start.Holding the key next to the receiver caused the stronger signal from the fob to drown out the weaker interference coming from farther away and the car started.

To wrap it all up.Your scenario of radio interference from LED's,or any other source for that matter,has nothing to do with what happens when the battery in the fob dies.
 

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2021 Crosstrek Limited, Magnetite Grey, 1.5" ADF lift, RRW RR2-V 15x7, Geolandar G015 235/70R15
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Your idea of what "shouldn't" happen and what does happen are two different things.You obviously have no idea how the system works.There are two different transmitters but a receiver is a receiver.Any and all receivers will listen for a signal at all times so that when the signal it's been waiting for IS transmitted,it will be ready to do what it must do.Then,there's the two transmitters.There's the active transmitter that transmits a constant signal for the keyless features such as the door locks and push button start.Then,there is the passive transmitter which is activated by pushing a button on the fob for remote start,door locks or to sound the alarm.It uses an RFID signal.That's Radio Frequency Identification.The key word is "Radio".The fob must transmit a signal over a "radio" frequency to be received by the car.It's impossible to produce a radio signal over any frequency without electricity.If the battery is dead,you have no electricity,no radio signals are produced and thus the car doesn't start as has happened to many people.If there is enough power in the battery to produce a signal and the fob is held close enough to the receiver to pick up that weakened signal then yes,it will start.

As for your Ram,I'm sorry that Dodge/Fiat cheaped out on their electronics and didn't properly shield them from interference.However,there is no 2nd receiver.The farther away the fob is from the receiver,the weaker the signal will be when it reaches the receiver.If there is a source of interference,such as your LED's and the fob is far enough away from the receiver,the strength of the interference will drown out/jam the signal from the fob and the car won't start.Holding the key next to the receiver caused the stronger signal from the fob to drown out the weaker interference coming from farther away and the car started.

To wrap it all up.Your scenario of radio interference from LED's,or any other source for that matter,has nothing to do with what happens when the battery in the fob dies.
Incorrect but believe what you want. You are confusing the term passive RFID to mean pushing the button on the fob to unlock the door for what Passive RFID actually is, a simple google search for passive RFID tags can clearly explain them. You also have your terms backwards, active keyless entry requires you to push a button on the remote essentially the user has to actively perform a function on the key fob, passive keyless entry or PKE requires no "action" with the fob making it passive, but neither of these terms have anything to do with what Passive RFID is. Passive RFID requires no power source within the key fob, which is why it's a secondary back-up in the key fob and has to be within inches of the push button. They use a magnetic field from the transmitter/receiver to induce a current within the tag (faradays law) the induced current will generate the signal hence the reason the fob has to be so close to function yet requires no internal power source. This is the same method used for passive RFID locks on buildings. Employees badges have no batteries in them, when the badge is next to the receiver the magnetic field powers the passive tag, it generates a radio signal and the code is read and the door unlocks same thing going on in the car. 9-17 in the owners manual will explain how to start your car with a dead key fob. I know I know you're going to say it only works if there is still just enough battery power left to produce a weak enough signal if it's close enough it will start the car. So I removed the battery from key fob (section 11-46 in the manual) and used the fob without a battery even in the fob to start the car, perhaps Subaru barely started using LF passive RFID (the oldest form of RFID) in their key fobs for the 21 model year. But please tell me more about how I have no idea how the system works.
 

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2021 Magnetite Premium 6MT
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Discussion Starter · #25 ·
Thank you. And maybe another stupid question, does the autel tool only work with autel sensors? Or would I be able to use that with any sensors in the same frequency and when swapping back to oem wheels/sensors?
I was able to read my stock Subaru TPMS, not sure if it works with other (non-Autel) aftermarket units.
 

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I have also been successful with using my Autel hand held TPMS reader on various OEM and aftermarket brands of sensors, great piece of kit.
 
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