Thread: Adaptive Cruise Control Slows Dramatically

The savage braking will be because it thinks that you're about to hit the vehicle because the radar unit isn't aligned correctly. The bumper will likely have to be removed to adjust the alignment. Press the accelerator hard when unwanted braking occurs to over-ride it.

To revert ACC to normal CC, with ACC engaged try holding the reduce distance button for 2-3 seconds after the distance has reduced to minimum. It works on L405s so probably also on the D5.

I certainly don't have that problem.
Mine behaves as I think it should.
You only have to just touch the accelerator to override the ACC

But how much does it take to override the braking? Perhaps not a lot but I needed quick acceleration to stop the vehicle too close behind from running into me when my L322 decided to brake hard at 100 kph when the vehicle in front stopped not quite fully off the road on a RH curve. I couldn't push the accelerator pedal far enough through the floor for my liking.

My MY18 HSE did similar things, all random and I never found an explanation or fix. 99% of the time the car behaved itself on ACC.

My MY22 Touareg does odd random emergency stops too.

There is something wrong.
Whenever running on ACC I find you have to be very careful to anticipate what the cars in front are doing at Y junctions etc where minor roads split from the highway. Until the ACC recognizes the car in front is not on your section of road it will brake to keep its distance. Just lightly applying the accelerator then keeps your speed and avoids braking. Obviously if your hard up against the vehicle in front it will become more interesting.
I normally use the default 3 distance separation and often 4 on open roads. To close the distance before overtaking etc, I’ll normally just use the accelerator to override the ACC and close the gap.

ACC aside, do you have emergency braking enabled? I had to turn this feature off in the D5 as I was risking a heart attack with all the false alarms. SWMBO screaming with fright from the passenger seat did not help (my heart).