04 LS430 Bluetooth: no audio on calls

[Antharro]

Simple problem, hoping for a simple solution.

Phone (OnePlus 6) is paired with the built in Bluetooth. If I make a call, the other party can hear me, but I can't hear them at all. Not even a whisper. I've been into the hidden settings menu to check the Bluetooth volume wasn't turned down - it wasn't. I get a beep when I adjust the on-screen volume control so I assume the amp is working.

Any ideas?

[BigBoomer]

It may be a problem with Bluetooth V5.0. I've heard of quite a few in the US having Bluetooth problems with iPhone8 and later, and that was the first Iphone to adopt Bluetooth v5.0. I have a 4 year old Honor 9 and that uses Bluetooth 4.2 and works fine with the car, although I don't connect to the cars Bluetooth.

Since I connect my phone to the car via the BlueMusic module to play music, I  use that to hear whoever I am talking to when on a call, and the mic in the phone seems to pick my voice up nicely. That said, I rarely take calls when in the car and almost never make them, unless parked.

Hope there is another solution, but you are connecting a 2018 phone with a 2004 car.

[jonthetourist]

I upgraded my Honor 9 to Honor 20Pro (fabulous camera!) which uses Bluetooth 5 and is still fine with the car. 

I appreciate that doesn't help much - sorry!

[cruisermark]

Just ensure the audio unit is powered on - just an idea

My Iphone SE 2020 connects and works fine

[BigBoomer]

Not Bluetooth 5.0 then 
Could be aptX HD (AAC) or another Codec that the LS is too old to recognise causing it, but normally Bluetooth negotiates a common Codec during the pairing process.
To test different settings, enable Developer Mode on your phone (https://www.bestusefultips.com/enable-developer-options-in-oneplus-6/) and go to Developer Options in the Settings menu.
There are a whole variety of Bluetooth Audio settings in there that you can switch on/off.
Try them one at a time and see if they fix the problem.
You will need to re-pair after each change.