Troubleshoot Key Fob Receiver / Antenna / Module

[TheNicestGuy24]

I have a 2011 SR5, no nav, no jbl, no backup camera. Convenience package included (sunroof, running boards, 120V outlets).

I bought this used 3 months after original owner sold it back to dealership they purchased it from (2K miles on it when I purchased).

I was given 2 OEM key fobs with the SR5. One was put away and never used in case I locked keys in or lost, etc.

About 3 years ago I noticed that sometimes my fob would have to be closer to vehicle to work, then eventually it came to the point where I had to press the unlock button 15 times before it would sense it.

Replaced with new batteries, same scenario, also the other fob that is never used experience the same issues.

Got voltmeter, batteries are 3v, the fob I normally use with new battery was hovering at 3.0v, the one that I never use with original battery is still at around 3.4 volts.

After a few months of it taking many many times hitting the button to work, it just complete stopped working altogether. Now I can't remotely unlock, lock, or use the panic button on either remote with good working batteries.

I assume that either the receiver, the antenna, or the module is bad, but I have no idea how to test any of these things.

I do have access to hook up my laptop to OBD plug under the dash, but I have really only used it to reprogram for replacing a bad OEM TPMS sensor on my Camry. Other than that I have no idea how to use it really. (not sure if I can name the software on this forum and not looking to break the rules, just need help with key fobs)

Any ideas on how I could test this stuff to figure out which component is bad? I just want my key fobs to remotely work again without giving the dealer $1000+

EDIT:: I searched on this forum for days and almost everyone issue was bad batteries and nothing on gen 5 about testing these components that I found

 

[nglayton]

What do you have in the cargo area?

I believe the receiver/antenna is located on the drivers side rear wheel well area.

I know after I mounted my ARB drawers, the range was greatly diminished.

 

[TheNicestGuy24]

Ok, so this may be confusing but follow along.

This afternoon with both fobs almost touching the 4R, neither fob would do anything, holding any of them, clicking any of them on either remote, nothing.

I took both fobs to local auto parts store to use on their fob testers, the issue was most of the stores testers didn't' work and the one that did they said was hit or miss. A guy that worked there said his GF had a 2018 corolla that works with no issues and their device never detects it as working.

The every day fob that I normally use that has a new battery that reads good voltage gets no signal at all at the device, doesn't light the device up, but the one that I keep in drawer with original battery gets a light green signal from device like it is weak.

The battery pack I bought a while back was a 2 pack, one of which was never touched. So I took the 1st new battery out of my normal every day fob (the one that wouldn't light the device at all) and put the 2nd new battery in that had never been touched, tested it against the device, showed a rather bright green light.

I then took both fobs out to the truck, both work most of the time now. It might not catch it one time every so often, but seems to work great for most part.

BUT KEEP READING!!

Now understand that I haven't touched the original battery in the fob that stays in the drawer and it also wasn't working earlier in the day, but after testing with said device at auto parts store it is now working too on the exact same battery that wouldn't work earlier in the day, like WHAT??

So I get home and decide to test batteries with volt meter, the new battery that wouldn't work in the my everyday fob reads 3.09 volts. The 2nd new battery that I then swapped to in the parts store, which then worked, reads 3.02 volts, but that is the one that works and it is lower voltage, what????? I then take out the 2nd new 3.02v and put the 1st new 3.09v in, which earlier today wouldn't work at all right next to the truck and it now works from inside my house, WHAT???

I also have the original Panasonic battery from my every day fob that I changed to new a while back, so for testing, I check it, it reads 2.94v lowest of them all that I have but it also makes sense as I carry it every day for many years, I then swap back to that original 10 year old battery which is what I originally thought was giving me the trouble a while back, and it works from inside the house now too.

None of this makes sense, so I then assume, my volt meter batteries are bad, put new 9v in, same readings with new battery in volt meter.

Sorry for the super long post but wanted to get in everything that happened.

I have no idea why it all the sudden works now, with ALL 4 batteries that I have, the 2 new ones an now the 2 original 10 year old batteries as well.

If anyone can explain the witchcraft that has happened her that would be awesome.


EDIT:: I also want to stress that my fobs have not worked AT ALL for at least 1.5 to 2 years now. Hence the witchcraft. The 2 pack battery was purchased just before they stopped working completely 1.5 or 2 years ago.

EDIT 2:: A day later and I have noticed that even right beside the truck it might take 2 clicks to unlock. I did talk to a service guy that works at a Toyota dealership and he said that most of the time when it fails completely and won't work, the device that usually goes bad is the one behind the fuse box under the dash. He said you have to pull the fuse box out to get to it, I have not investigated that as mine is still working for the most part. Just wanted to give this info to maybe point someone to that device first if theirs is complete failure.

 

[bboy626]

What do you have in the cargo area?

I believe the receiver/antenna is located on the drivers side rear wheel well area.

I know after I mounted my ARB drawers, the range was greatly diminished.

This post zero’d in on where to look after my key fob stopped working. DIY a sub install and sound dampening mats months ago, and failed to plug the wire back into the module. Thank you!

 

[warriv]

FYI I had the same issue on a new 2022 4runner, after various mods and changes. The reduced range makes sense given the sleep platform etc but I have also intermittently had this same behavior you described.

Fob battery levels were fine just like you. Car battery level was fine as well; charged it some more for good measure and still no luck.

Ultimately the hint I got from your post was that the behavior was pretty random and unpredictable and not really correlated with everything else you were trying. Which to me basically means there's some bug in the computer's code, or some stuck state that needs a reset to fix. So I disconnected the battery and left it a bit before reconnecting, and sure enough that fixed it.

Time will tell if it's fixed permanently or not, but at least I have a workaround now when this happens.