Have single FOB#2 and range is suddenly terrible
 

Hi all, first time user from Chicago. I have 2010 MDX purchased as a certified pre-owned in 2012.
I lost the #1 FOB over 3 years ago, and have been using the #2 successfully ever since.
I replaced the battery in #2 a couple years ago when the range went down and it worked flawlessly since then.
About 3 months ago, the range in #2 plummeted again (though much more suddenly this time) and I figured it was a battery issue.
I can only stand close to the driver or passenger window and the lock/unlock feature works sporadically - I have to point the FOB at the driver seat (I think the receiver is in the fuse panel in upper left driver leg area). The FOB-under-the-chin method does not noticeably improve the range.

So I replaced the battery (CR1616), and no improvement.
I pulled battery and put a new one in after checking both batteries for voltage, they're both strong (~3.2V). I also verified the contacts in the FOB are strong, in contact, and gunk free.
Still same issue.

I've read that re-programming is a possible solution.
And I've seen that the receiver might replacement, though I don't understand how that make sense, because it DOES work, if just unevenly.
Do FOBs get weaker over time? (besides battery issues)

Can anyone recommend next steps?

Thanks!

When I purchased my 11 MDX used in 2014, Driver 1 FOB was very weak and the range was pretty much at the door handle. I had Driver 2 FOB to compared to make sure it wasn't a MDX issue. I did the battery replacement and zero change in range. Lucky for me I was still under the factory warranty and it was replaced. Both fobs are working normally after +5 years.

Any chance you are still under the CPO warranty or have Acura Care?

Thanks for response!
Purchased in 2012, I'm pretty sure the CPO warranty is done.
I had Acura Care 5 year extension, it expired in 2017.

Hoping I could find reference to where exactly the receiver is, just to check for connection (whether or not seated, if that's even possible).
But I have not seen anyone describe doing any changes (much less the location) to the receiver.

Was thinking I might try to find an aftermarket #1FOB to see if I could program it, and get a locksmith to key it from FOB#2. That might be a less expensive way to see if the receiver is a problem since I lost FOB#1 a while ago.

I've seen some references to possible issues:
* the wiring harness in the driver side door between the receiver (and other control unit) and the panel
* the receiver unit itself inside the driver door (link)

I pulled the boot off the wiring harness and everything appears to be fine. Of course, if there was a wire disconnected, I would be experiencing things not working.
Other than taking to a dealer for a diagnostic, I don't know how to determine if the receiver is bad or failing. This seems more likely since the range is so poor.

I see that new FOB#1 (part number 35113-STX-A40) is about $90 and I would guess keying is about $50.
I found a local service here in Chicago that will provide the FOB, key and programming for about $150.
So I am going to try the new key, since I need one anyway - and see if resetting/reprogramming helps at all. But again, my guess is that the receiver is going bad.

Doesn't hurt to have a spare FOB and you can see if FOB#2 is bad or the issue is with the wiring harness with the new key. The only other option is to go aftermarket alarm. The existing OEM FOB+key would only be needed to start the MDX. You can then add other features like remote start, motion alarm, GPS tracking, etc...