Smart Entry detection range only 3 inches

Hello! New to the forum, searched up and down the Gen 3 pages with zero luck so I'm making a post.

I have a 2013 Prius Model II, and a while ago (possibly more than a year) the Smart Entry system key detection range fell of dramatically - to the point where I have to hold the key almost against the door handle for the touch lock/unlock sensors to work. I just tested the range again tonight by trying to use the lock/unlock sensors and also seeing when the dome light turns on due to proximity.

Things I have tried:

1. Replacing the key fob batteries
2. Trying a different fob (also replaced the battery in that fob)
3. Opening the door panel, unplugging the antenna/oscillator, turning the car on and off, reconnecting it (that was in hope of triggering an automatic re-calibration. I was desperate!)
4. Turning the smart key system off and then back on

Things I have made sure of or ruled out as causes:

1. The fob isn't next to a cellphone or otherwise isolated
2. The second fob is far away from both the car and first fob
3. I think I probably would have seen other issues by now if the 12v battery health is the cause

Things I am considering:

1. Swapping out the door handle antenna oscillator for one I find at the wrecking yard. I can accomplish the removal/installation easily enough, though I'm worried that could fudge up my whole keyless entry system
   
2. Hitting up ebay for a techstream cable and software - the dealership said they could re-calibrate the sensor, which means maybe I could? Not sure if it would be an option in techstream or directly on the controller ecu that powers it (I think?)
3. Just giving up and handing the dealership all of my money

Tinfoil hat land:

When I went in to take a look at the sensor itself it looked like someone had already opened the plastic inside the door frame. Then the clip holding the antenna cable in place was loose, and when I disassembled the handle I noticed there was a white chalk mark on the back of the sensor. Just like chalk marks I see many people use to mark bad parts.​

Did they swap this out after a previous service to screw me over? Probably not because I would have noticed right away. But this is how desperate I am!​

What I am asking for:

1. Do you need any more information to help solve this problem?
2. Given the information supplied, would you recommend "Things I am considering" option 1, 2, or 3?

If you made it to the end of this post you deserve a medal. If you have an answer you deserve a national holiday.

 

Also, if someone with techstream could confirm whether or not the antenna/oscillator calibration is an option in the program I would really appreciate it.

 

7 years/exactly as old as the car. I'll look up the wheres and hows of load testing - will my dealership do this?

 

From what I've seen I don't think I'm comfortable load testing my battery on my own. I'll find out what it costs to get someone to do it, but if it's more than $50 then I'll be trying to replace the sensor and getting a copy of techstream as I can do both of those for less than $50 each.

I'll keep this thread updated with how this goes.

Also, I promise I am responding quickly, but my replies sit in moderation for a bit (which I totally understand - can't be having bots spam things constantly).

 

I just voltage-tested the fob battery, it's sitting at ~3.05V so all good there. Thank you for suggesting a way to confirm something I had just assumed.

I'll grab a repair manual now as well. This is getting even more interesting, really crossing my fingers for a simple-ish solve.

You just reminded me of another assumption I made. I need to find a picture of the antenna/oscillator part. There is a (I assume silicone) sort of solid gel encasing the circuit board of the part. The silicone in mine looks brown/dingy - I wonder if it burned out or if they all look like that initially/over time.

 

Oh. my. gosh. I am an idiot. I was thinking hybrid battery = 12v... Well that makes this a very easy first step/thing to check. Apologies for not knowing what the hell I was talking about!

 

Probably - definitely since we've owned it. I took a look and it has a "distributed by Toyota" sticker on it, and I know I wouldn't get a battery from them.

I tried a thing, maybe stupid. I hooked up my portable jumper and turned it on, figuring it might compensate for anything going badly with the 12v. Fob detection area was unchanged.

I'll still get the 12v tested and replaced if necessary, but I'm less hopeful this is the root cause of the fob issues. Nonetheless, thank you for bringing some maintenance I was slacking on to my attention!

 

12v load tested at AutoZone, they said it looks perfect! Next step will be replacing the antenna/oscillator since I think techstream probably doesn't have calibration options.

I'llupdate after the swap!

 

Part swap completed (antenna/oscillator in handle swapped with one from the auto wrecker) - range exactly the same on both. Womp womp, probably not the cause. I guess both could have failed, but if it were common then this fix would be more easily found on the internet.

Good news for people who aren't me:

• if this has happened to you then you can look here for what won't work
• swapping the antenna/oscillators doesn't seem to mess with the keyless system at all, so you can consider them swappable. do not know if this was general knowledge before.

I think my next step would be to break out a breadboard and a multi-meter and see if the right amounts of power are going to the antenna, but then if the voltages were wrong I'd have to futz with some parts that are above my pay-grade (zero dollars per hour). Also the fix would almost certainly exceed the budget for this project.

Last ditch effort - there's a zip tie that looks like a home-fix on the cable plugging into the handle. I might take it off and make sure the leads are in good condition/not shorting because of rubbing/contact with the other leads or the zip tie.

I might, miiight, ask the dealership or a shop to diagnose this depending on their rates.

Past of me still wonders if techstream would be able to help with this. Might just pick up a copy out of curiosity at this point.

Next steps:

1. peeking at the cables
2. hoping someone pops into this thread with an answer/something to try
3. maybe getting a mechanic to take a look

 

Hmm, I'll grab a brand new one from the pack to see, and maybe a new pack if they all seem low-ish. It'd be funny if this was all because of a bad pack of batteries!