Haven't posted here in a while. Sorry about that. I need some extra brainpower to help debug / troubleshoot my phone talking to my car. This one's a real head-scratcher.

Up to this morning, everything worked just fine. 2017 VW GTI, AA Wireless (v1), running 3.5 firmware, Pixel 9 Pro phone running the latest Android 15 and Android Auto version 13.4.645054-release. I drove to see a friend for lunch, using all of the above and it all worked properly. Got back in the car (*), and then total haywire.

Blank screen in the car, occasionally popping up "Reading USB" but making no progress. On the phone, "Android Auto is searching for the car".

So I tried a bunch of troubleshooting. Plugged the phone directly into the USB for the car. Didn't work! Discovered that USB was in charge-only mode so switched it to allow for file transfer & Android Auto. Still didn't work! Tried using Bluetooth. And that's where things get weird.

Phone screen: "Problem connecting. Turn device off & back on"

Car screen: (After selecting my phone on the Bluetooth menu) "Pixel 9 / Unable to connect to mobile device. The device AA Wireless is already connected through Android Auto."

I tried all the remaining obvious things after that. I told the car to forget the phone. I told the phone to forget the car. I disconnected the AA Wireless box. I power cycled the phone and the car, multiple times. I redid the Bluetooth pairing. I did an upgrade from the 3.5 firmware to the newer 4.5 firmware. I tried the USB cable again. Nothing worked.

So, something is really messed up here. I'm particularly unsure how to interpret the message in the car's screen, refusing to connect to my phone. Somehow, my car has associated my phone's Bluetooth with the AA Wireless device, even though I had it completely disconnected at that time. Like it refuses to talk to my phone any other way. This issue persists even after powering the car and phone, both down and back up again.

I'm usually pretty good at this sort of troubleshooting, but this time I'm stumped. I even pulled the logcat from the phone, but I don't really know what I'm looking for, and there's nothing obvious jumping out at me.

(*) This is a stretch, but here's an additional detail that might matter. I took my car to a carwash. Everything was working correctly while I was waiting in line. After it came time to hand my keys to the staff, I turned the stereo off but the car was still on while they were working on it. I went inside, which means that my phone and my car were presumably in and out of radio range. After this, the haywire behavior began. So, it's possible that something about this situation triggered the bad state of affairs.

When you "powered down" the car, did you disconnect the battery, then wait a few minutes, and reconnect it? Or did you just power off the radio? A battery disconnect would reboot all of the myriad computers in the car and possibly solve the problem or at least give a few more paths to investigate.

This is a third party device?

Powered down = turn car "off", then open the car door. This seems to cut power to most of the car's systems, e.g., turning off the stereo. I've let it sit overnight and will try again today. After some Google searching, it's also possible to hold down the power/volume knob for 10 seconds to force a reboot.

AA Wireless: if you have a car with USB Android Auto but not the newer Wireless Android Auto, this is one of the gadgets that's seen as a solid alternative. There's also a cheaper one from Motorola, which I originally had, but it flaked out and died.

Some additional background and then a few hypotheses:

The original Android Auto ran over USB. The idea was that your phone could take over the screen in your car. Also, there was some amount of extra metadata, like whether your headlights were on, as part of the protocol. At least with my car, one of the problems with this was that the physical USB connection became unreliable. I'd go over a bump and it would go blank for a second then reconnect.

The newer wireless variant is the solution. I don't entirely get how they managed this, but if you're in a car with wireless Android Auto, integrated from the factory, then the initial Bluetooth pairing process will (sometimes) also lead to a wireless Android Auto pairing. I believe it then uses local WiFi for moving the bulk data around. In other cases (rental cars are awesome), you do initial setup with a USB cable, and you get a Bluetooth pairing automatically. Subsequent times you get into the car, it's automatically using wireless Android Auto.

So, back to the AA Wireless box. They were originally an Indigogo solution to adding wireless Android Auto to cars, like my VW, which only had the wired version. Where the cheap Motorola adapter just does "pass thru" of the protocol, the AA Wireless software has a variety of toggles in it that explicitly work around bugs with different cars. So far as I can tell, it's the best solution to my problem, and it worked without issue, for years, until yesterday.

Anyway, enough background. I'm really curious about that error message I got on the screen in the car. "Pixel 9 / Unable to connect to mobile device. The device AA Wireless is already connected through Android Auto." When my AA Wireless is disconnected and yet I try to do a Bluetooth pairing, this still happens. The hypothesis I'm coming around to is that the VW headunit has some concept of Android Auto "overriding" Bluetooth from the same device, and it's gotten into a weird / buggy state where it can't recognize that the Android Auto connection ain't there. The test for this hypothesis is that I need to reset the head unit. Maybe that's just the ten-second press of the power button. Maybe that's disconnecting the battery. TBD.