My iPhone 4s shifts from car (Lexus 350RX 2012) speaker to phone speaker and back constantly when I'm on a call. I have erased the pairing between the phone and the car and re-paired it, I have also re-set the phone to no avail. Lexus says my car firmware is up to date, but I read in some apple forums that the bluetooth firmware needs to be updated. it has to do with Bluetooth AVRCP 1.4 compatibility. My Lexus dealer claims no knowledge of this. This is really frustrating.

 

Well iOS 7 was just released by Apple today. I have been using iOS 7 for a couple months, as i'm a developer. I haven't had an issue with my iPhone 4s. HAve you tried someone else's iPhone? it would be the quickest way to rule out your Lexus as being the issue.

 

Do you have any other phones paired? It appears to confuse the system if there's more than one phone paired, but not necessarily in range.
I don't have bluetooth dropping off with iPhone 5, but I do have to reboot the system often enough to re-initialize itself with the phone. Its bluetooth audio is also a hit or miss.

 

Thank you for responding. Although I'm going to switch to IOS 7, I resolved the issue by re-setting my phone in the car and turning it on again. I believe now this is an issue with some iPhones, as people with other car brands have been reporting the issue on Apple support sites. Sorry Lexus!