I do have the same problem with a Galaxy S8 and bluetooth car pairing, immediatly after upgrading to Android 9 (security patch level: February 1, 2019) on March 8.
Problems are random.
1. Most often the car is able to pair with the phone (i) only for phone calls, no audio streaming; (iI) it is not able anymore to synch with the contact lists; (iii) the list of recent calls show strange entries
2. Very often the phone goes on connectiing / disconnecting every 10-20 seconds. It seems that this does not happen if, on the phone, I enable pairing only for phone calls
3. Sometimes the phone does not pair at all
4. Sometimes the phone does pair with the car, but when I list the recents call, the car reports an error messaqge about a missing folder on the phone
Pairing with my bluetooth headset works without problems.
I have seen this problem reported since December 2018 on other forums (for non-Samsung devices)
I had this problem, and think by unistalling Samsung SmartThings it seems to stay connected now....so far!
I think it is that app that is causing the problems for me, with constant connect/disconnect in the car - impossible to make a call since the update to Pie. I was also considering getting rid of this thing (S9) and getting something else, lets face it I had a phone before the first iphone was made that would stay connected to the car!
Same issue: Just after the pie-update, my S9 kept on dis- and reconnecting to my car when I wanted to connect via bluetooth.
After some annoying weeks, now months, and endless (un)pairings/reboots later, the only temporary fix for the AUDIO function was for me to disable the phone-connection in the bluetooth menu. Result: Music possible, phone killed.
But this also shows that there is definitely something wrong with the phone connection. Which is ridiculous considering the fact that the S9 should be one of the top smartPHONES... I won't quote the price of the car (2016) and its infotainment here...
Come on Samsung and Google, pls. do something...
Removed it and unpaired phone then repaired.
Same old issue I am afraid of continual connect and disconnect making it totally unusable. Perfect before A9Pie. Samsung support would appear to be ducking this a treat and totally failing loyal customers..wouldn't touch them again. Their solution...get someone to look at it at a service centre 7hr round trip..for a problem they KNOW they have. Nice customer treatment Samsung...hope you read these posts and get your act together..quick enough to take our hard earned money. Sorry long answer and thanks for the suggestion will try anything !!!
thought I'd solved it and mine today disconnected again while on an important call!
I may either get an iphone and take the loss on this one, or go back to my SGH-Z720 from 2006 - at least that one works!
I don't get why there is no rush to solve this from the update, or least give people the option to go back to Oreo - that worked fine.