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Thread: Adaptive Cruise Control Slows Dramatically

  1. #1
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    Adaptive Cruise Control Slows Dramatically

    When travelling behind a car using Adaptive Cruise Control and the car moves to another lane the ACC triggers the brakes dramatically. Over dramatically. It usually occurs when doing 60-80 km/h.
    It’s so dramatic that the car slows to less then 30 km/h. I now have to hover over the Cancel button when using it. Does anyone know if there is a fix or software update? I’m in a Discovery 5. 2019 model.
    I’m also wondering if there is a setting that defaults ACC off when engaging cruise control.

  2. #2
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    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.
    MY12 RRV 4.4 TDV8 AB, +LLAMS, +e-diff, +ACC stop/go. Produce LLAMS for LR/RR, Jeep GC/Dodge Ram
    VK2HFG and APRS W1 digi

  3. #3
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    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
    D2a (Sold)
    MY17 D5 SD4 SE (Sold)
    MY19 D5 SD4 SE (with all the options I want)

  4. #4
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    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.
    MY12 RRV 4.4 TDV8 AB, +LLAMS, +e-diff, +ACC stop/go. Produce LLAMS for LR/RR, Jeep GC/Dodge Ram
    VK2HFG and APRS W1 digi

  5. #5
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    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.
    Touareg CR 210TDI 2022
    Disco 5 SD4 HSE 2018
    Disco 4 3.0 SDV6 2014
    Disco 4 2.7 2011
    Disco 3 V6 SE 2007

  6. #6
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    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.
    D2a (Sold)
    MY17 D5 SD4 SE (Sold)
    MY19 D5 SD4 SE (with all the options I want)

  7. #7
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    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).
    Touareg CR 210TDI 2022
    Disco 5 SD4 HSE 2018
    Disco 4 3.0 SDV6 2014
    Disco 4 2.7 2011
    Disco 3 V6 SE 2007

  8. #8
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    I have Forward Alert enabled and have become accustomed to expecting the alarm to sound and it appears that my wife is also no longer surprised by it, judging by the cessation of the comments. Maybe I don't give turning vehicles a wide enough berth mostly in traffic but I have it enabled just in case it helps with emergency braking if a roo jumps out after dark. However IIRC the radar unit doesn't see animals so perhaps FA is of little use.
    MY12 RRV 4.4 TDV8 AB, +LLAMS, +e-diff, +ACC stop/go. Produce LLAMS for LR/RR, Jeep GC/Dodge Ram
    VK2HFG and APRS W1 digi

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