Norskie

Alright, I'm starting to get annoyed.

My 2015 SQ5 w/90k miles is not consistently reacting to touching the door handles to lock and unlock.

There are no codes (per OBD11) and it's consistent between both front and rear doors (so I don't think it's a specific handle sensor).
Pressing the FOB key works fine, as does starting with push-button, and opening the rear hatch, so the fob is able to communicate with the car.
I've put a fresh battery in the FOB.

It started to go wonky in early December, doesn't matter if I park outside or in the garage.

An oddity I noticed last fall when hand-washing it, was that water over any of the door handles would lock/unlock the car.

Presumably there is a sensor somewhere in the car; does anyone know where it is? If anything I can unplug it, clean the contacts, and plug it back in. Or replace it.

spijun

Maybe this can help

Norskie

Excellent! Thank you, that gives me a place to start.

silver_tt

I don't have issues with the sensors not working on my 2014 2.0T Premium Plus with the same feature but FWIW when I wash the car by hand with a sprayer and shoot it with a heavy stream of water (instead of mist for example) sometimes it locks the car (beeps, mirrors go in, etc)... presumably due to one of these sensors. Doesn't bother me but just FYI since it's likely not related to your issue since mine does it but my sensors are fine....

SMac770

The sensors are in the door handles. They are prone to developing issues over time. I've replaced two already, and a third is now flaking out. But I had a DTC in all cases, at module 05-access/start authorization.

If you don't have any handle sensor DTCs, it could be simply a problem detecting the key fob. Fob detection via RFID for keyless operations is a completely different implementation than the RF transmitter / receiver used by the fob buttons.

When you wash the car, you have the fob on you? I leave it in the house so the handles are not constantly toggling.

When I go to the hatch, if I lead with my left side to reach for it, it won't activate, because the key is in my right pocket. I turn my right side towards the car and then it opens. So could be something like that.

Norskie

Using Spijun's diagrams I now know where the antennas are. I did some troubleshooting.

The next time it didn't work, I was at the rear driver door trying to lock it. So I held the key in my left hand and extended it towards the front driver door and tried the rear lock again, and it worked. Moving the key around, I found there was a 'dead zone' by the rear driver door. Thus I suspect there's something wrong with the rear driver antenna, and the intermittent nature seems to be due to whether I had the keys in my right or left pocket. Time for a new antenna .. or if too expensive I'll swap it for a the front passenger antenna (which never gets used).

Yes, I'll need to move the key to the house next time I wash it!

HZ60

You can also leave the fob inside the car while you wash it to keep the locks from going nuts. Works for me.

Norskie

Well, it wasn't the antennas.

I'm back to square one ... all the door handles are unresponsive until I unlock the car with the fob, then they become responsive again.

I've got a new battery in the fob. There are no stored codes or errors with the handles (besides, they're all unresponsive, not just one).

Hm. Odd things happen batteries start to go ... I wonder if the car goes to 'sleep' when voltage falls below a certain threshold? But I've never had any issues starting the car, at any of our subzero temps. I'd hate to throw a battery at it only to find out it isn't the battery.

spijun

It is possible that the problem is with the battery
The system is designed in such a way that when the voltage drops, it turns off all the necessary systems to be able to start the car.
Comfort access constantly emits a signal, so it consumes the battery

Norskie

Yeah, that makes sense.

I mean measure battery voltage, do you know the threshold below which it will do that?

Do you know if there's a way to verify it's going into 'battery conserving' mode?