Adaptive Cruise Control not resuming speed after reduction

[BoeingPete]

I have a 2 month old 24 plate Yaris Cross Design. I drive it once a week to London (100 mile round-trip) on the M1 and use the ACC and Lane Trace alot, but recently noticed that sometimes, after my car has slowed down because the car Infront has reduced speed, when that car then accelerates away my car only continues to decelerate until I intervene by applying the accelerator. Then it picks up, accelerating to the selected ACC speed - usually 70mph or until it has matched the speed of the car Infront. I've tried increasing and decreasing the spacing but that hasn't had any affect. Is this likely to be a fault in the system or is there something I might be missing when using ACC, given this is the first time I've ever used ACC?

[Cyker]

That's a bit concerning... I've not experienced it in my one, but mine is an older revision and I tend to manually disable the ACC if the car in front slows and then re-engage it when they pull away, as the ACC in the early revisions is very unrefined and tends to close on the car in front too closely before suddenly braking really hard.

However, I've seen posts by people in newer revisions of other models (I think the Corolla and RAV4) who have reported this same behaviour...  

Assuming the delay wasn't just the car waiting for the gap to build again, report it to your dealer and maybe Toyota UK, maybe see if there is a firmware update for this...

 

[Ralph H]

My 24 plate doesn’t do that, in fact it accelerates too fast for my liking when the gap increases. Sometimes undertaking cars in lane 2. 

[Knorton]

My 24 plate does'nt do it either. Though compared to the 23 plate one I had the newer one sometimes will pick up on larger vehicles in other lanes and hold the speed down.

Kev.

[Mushu84]

Hi Peter,

 

Please check what settings you have on radar distance, as mine if I have it on long distance,  will not accelerate as fast as I would wish, but will keep keep decelerating as the radar sees the car in front is to close and I need to wait a LOT of time for it to pick up 

 

On the motorway I like to keep it on mid distance as it better response from the radar

[HarryW2024]

Not used it often in mine tbh, but when I have I found it pretty good.

I set it to maximum distance and minimum response/acceleration ( if I recall there’s 3 levels for response/acceleration buried in the settings not on the steering wheel). What I find is when you slow down and pick up speed again it doesn’t match the car in front by giving it the beans but gently comes back up to speed again. Suits me…

[Hadrian1]

Setting for long distance is fine unless you have someone close behind.

[HarryW2024]

40 minutes ago, Hadrian1 said:

Setting for long distance is fine unless you have someone close behind.

Agree it can be a problem for a car behind if they are close.

the distance settings at 60mph are set out below.

 

using the 2 second rule you need to leave approx 50m between cars at 60mph….

[BoeingPete]

Can't name you all but thanks so much for the comments/info/guidance. Some really helpful, stuff there!!

It doesn't happen every time, and seems to occur when the car has braked quite heavily in heavy motorway traffic, and it did cross my mind that it could be picking up on vehicles in the nearside lane, which tend to be slower to pull away especially when the vehicle directly infront of me pulls away quickly. I have played a little with the vehicle-to-vehicle distance and need to look closer at that but having read all your comments and recalling the conditions that existed when it happened, I am now thinking that if the vehicle-to-vehicle setting is set on max distance (which it has been) with a slow acceleration response (wasn't aware that could be changed but will check that out), given this problem usually manifests itself in heavy motorway traffic and my car has started to slow down when the car infront then pulls away quite rapidly. I'm just wondering that perhaps my car continues to slow down to increase the vehicle-to-vehicle distance (I've let it drop as low as 15 mph to see if it would accelerate before intervening) and in the meantime loses radar contact with the vehicle infront, or has latched on to a slower vehicle in the nearside lane. Hard to test all this while in traffic, but will monitor it for a few trips and take it to the dealership if I cannot identify the cause. A good starting point will be to see if I can change the response/acceleration. THANKS AGAIN EVERYONE 😀

[HarryW2024]

Go into settings> DRCC>Acceleration; select > 1 low, 2 med or 3 high (3 bars 1-3)

[HarryW2024]

Also I don’t think DRCC works below something like 20mph, so if traffic has slowed to a walk it probably has disconnected it and will not pick up again?

[HarryW2024]

Also thinking about it, once below 20mph and the system has disengaged you could try pressing resume (RES), to see if it then picks up again even if you’re below 20 at the time…

[dash]

Mine resumes from standstill in tailbacked traffic (so long as not stationary for more than a few seconds the system stays engaged)

[Mushu84]

1 hour ago, dash said:

Mine resumes from standstill in tailbacked traffic (so long as not stationary for more than a few seconds the system stays engaged)

Mine does the same, I love using it in heavy traffic as I do not have to worry about it, maybe is a new safety feature? (for me would not make sense not to work)

My Yaris is 2021 and the radar works at any speed, in any traffic situation, canceling the standby mode if you stay for 10-20 seconds (I think, never measured) and then you have to resume from +button or press acceleration pedal 

 

[BoeingPete]

Yeh, when it's working properly it will stop when the preceding vehicle stops and will pull away on it's own if it hasn't been stationery too long, after that it needs a little nudge of the accelerator or a flick up of the RES button to get it going, and according to the manual that's all normal. Amazing feature to have especially when used with Lane Trace Assist while driving on a motorway.

When it throws a wobbly the RES button doesn't do anything but if I press the accelerator then she picks up and accelerates away on her own. The Adaptive Cruise Control light remains green. 

Harry W2024, after reading your post I found the DRCC setting and set it to HIGH and will see how it goes with that and  with the vehicle-to-vehicle maybe set to midpoint so the gap between me and the car infront isn't allowed to get too  big especially when the preceding car has pulled away quickly. 

It is an intermittent issue so the system evidently works, but I am hoping that it is just the combination of settings and traffic conditions/behaviour that is confusing it. If it persists then I'll be  taking it back to the dealer to check. 

 

[JasonM]

Hi Pete, I replied to your post on the Corolla forum from last week👍