Cruise control doesn't maintain correct speed
 

Curious if anyone else has seen this - after setting cruise control, it often maintains speed 1 mph lower than what it is set to. For instance if I set it to 74 mph, it will maintain 73 mph. This happens about 75% of the time with no traffic in front at various speeds.

https://cimg4.ibsrv.net/gimg/www.clu...19b1f6a862.png

I have a 2024 TX350 premium and my cruise control and creative cruise control does the same as yours, 1 mile less

Our TX does this also and our two Volvo’s do the same thing.

I’m wondering it’s one of two things. One is that they both use the same third party controller for cruise control. Two would be some regulation that says they can be fined if the traveling speed is higher than the set speed so they errr on the side of caution.

We’ll probably never learn the real answer.

Same on my 2025 TX.

Well glad to know it isn't just ours, have any of you asked the dealer to look into it or why it is that way? I've got an appointment coming up to have my ML sound system looked at and I might ask about it as well.

Can confirm..... annoying.

My Grand Highlander is the same - always 1 mph or 1 kph off.

My TX350 cruise control slows down a little when I go into a curve. Kinda annoying.

+1
You may also notice a 'curves ahead' icon that momentarily appears on the instrument cluster about the same time the car makes a speed/power adjustment in the curve.
You might see 'Deceleration Assist' and 'Dynamic Radar Cruise Control' to make 'Curve speed reduction' adjustments inside the Owners Manual [p.272, p.549 TX350]
I'm glad you mentioned this! I'll probably adjust mine the next time I remember.

Let us know if you can delete that slow down.

FWW I have a 2022 RX450h and most of the time it also cruises 1mph under set limit, but sometimes it "catches up"...

Good news. After I posted here last week my car was in the dealership for a number of things. When I picked it up, for some reason the cruise set speed and actual speed now match exactly. There must be some software update that they installed (even though I hadn't asked). Check it out next time your vehicle is in for service.

I was going to make a post about this too! I own a 2022 RX 350 Fsport and had it serviced for an airbag recall. Lexus gave me a 2025 Lexus TX 350 AWD as a loaner and I have this same problem. It is only showing me going 1 mph less than what I set it at even when going downhill. I took a picture of it too. Here it is. I have mixed feeling about this vehicle. I wonder what was wrong?
https://cimg2.ibsrv.net/gimg/www.clu...1a10a01908.jpg
It stayed at 74 mph for the whole 45 minite trip on highway.

There is a Curve Speed Reduction setting with High/Low/Off choices.

Follow up - tested the 'Deceleration Assist' and the slowdown in the curves was not affected.
Interestingly, I noticed the cruise control commanded speed and actual vehicle speed was the same for a time much longer than I have ever noticed before. You might even say it acted "normal."
Coincidence??? Perhaps some others could provide a few more data points if they make a setting change?
After having no effect in the twisties, I turned it back on because Im not yet certain what others systems it may interact with; Auto braking, stability control, collision avoidance, distance following, etc, etc, ....? Who knows.......?
Settings >> Driving Assist >> Driver Support => Deceleration Assist

Still toying with the menu sticks to find the 'Curve speed reduction' option.
Just a little more homework to do.....