Hey guys , I’ve got a 2018 a6 c8 40 tdi mhev and just noticed that the stop start is kicking in and out every say 10 seconds , also when I start it it says lane assist unavailable and pre sense unavailable , I had the battery’s tested and they said they was 13.3 v so the hybrid system is working ok ,any ideas what it could be ?

Has there been an actual diagnostic check to see if any fault codes flag up? 

Could it be an issue with the conventional 12v battery? 

No faults came up and typically when it was it the garage it never did it so they couldn’t find any faults they said that they had tested both battery’s and was fine , weird 

Does this happen immediately on driving the car?

Likely a significant fault or damage to your radar/windscreen/parking sensors damaged.

if not, does this happen more prominently after/during long distance driving or short distance driving?

If short distance driving, does this happen in heavy traffic or light to medium traffic conditions?

If heavy traffic conditions (start stop) it could be related to an intermittent fault with the your frontal parking sensors or windscreen being obstructed or damaged or requiring calibration.