DUTCH VanAtlanta

2015 Q7 3.0 TDI Prestige with 2,000 miles on the clock.

Did an all Interstate highway trip to Florida and back this week. The Cruise Control would shut off/stop working after using it for a while, and could not be restarted until I stopped the car, stopped and restarted the engine.

No fault codes show up in a VCDS/VAG-COM scan.

Dealer's Service Manager has no clue; and I'm not up for them doing a fishing trip to try to find this intermittent glitch. Anyone else have this problem?

smith2010Q7

Dutch to many problems are you sure you do not have a lemon?

On the 2015 I believe you have the ACC systems correct?

Some info:
If the circumstances temporarily blind or confuse the inputs the system will shut down for a while before resetting. So for example, did bright sunlight hit the camera (behind the rearview mirror) while the rest of the surroundings were very dark? Were you behind a short trailer (seen by the bumper radars) being towed by a car further away(seen by the camera)? If it gets confused, it well shut down and may say "No Sensor Vision". I think it has a timeout and then will start working again. Any attempts to set the ACC during the timeout will give you the error.

if the screen camera thinks the screen is too dirty and deactivates ACC, it normally says in the DIS something about "clean your screen"
- if the radar domes are dirty, that'll give the "ACC unavailable" error. I once had to clean them three times before I could get ACC working. I keep a bottle of water and a good quality cloth in the boot just in case.
- you can set the ACC when not moving. Put your foot on the brake and press the button on the end of the cruise control stick. You can then remove your button from the brake and the system is primed to go (within the default time out before it's disabled again).

Gavin0478

The ACC uses a sensor behind the grill filler plate.

Behind the mirror any sensors/cameras are for the lane assist and for the automatic headlight dipping.

I can photo these if needed.

DUTCH VanAtlanta

I am quite sure that I do not have automatic cruise control, nor lane assist nor automatic headlight dipping. Perhaps in Europe, but not in the US - at least not on mine.

DUTCH VanAtlanta

No ACC to my knowledge;and no error messages flashed. It just stopped working, and would not restart unless I stopped the car, shut off the engine and restarted it.

iconoclast

smith hit ever possible option if you have acc, if you don't you may have an issue with abs. if abs is faulty or kicking in cc will not engage. if you hit potholes or loose gravel cc will disengage but it should engage again once you manually set it again.

DUTCH VanAtlanta

No ACC. If the ABS were kicking in, would it not show up in the instrument cluster? The only way I can manually reset it is to stop the car, shut off and restart the engine.

Also, there are no fault codes shown in a VCDS/VAG-COM scan.

Definitely a puzzler.

iconoclast

the fact that there are no codes at all is what i find puzzling.
when am overinflated cruise control shuts off automatically from lost of traction or hitting pothole but there is no indication on the cluster i only realize because the vehicle slows down.

smith2010Q7

Cruise Control system on a Q7 without the ACC system is very simple to troubleshoot. On the latest vehicles fitted with electronic throttle control, cruise control can be easily integrated into the vehicle's engine management system Plus are system turns off is by the brake sensor, plus the switch on the steering wheel. The cruise control takes its speed signal from a rotating driveshaft, speedometer cable, wheel speed sensor from the engine's RPM, or from internal speed pulses produced electronically by the vehicle.

I will looking for a broken wire which it acts up when hitting a bump or gets wet. Plus a loose connector could be in the brake sensor, with a bent pin? Also a sloppy fuse not having a good connection. The list will have to be check one by one which can take a couple of weeks which I know you are tried driving a A4.

DUTCH VanAtlanta

My problems with the cruise control took place on a smooth Interstate Highway - no bumps. The weather was sunny and hot - no rain.

I will check the fuses.