tcarroll2

I have a 2007 LS460 and one issue I have, which could be costly unless I'm paying attention, is the cruise control does not perform automatic downshifting like my Honda does. In fact, my speed can increase by about 10-15mph going downhill, which a couple of times I've been lucky to realize my speed is increasing and downshifted manually and sure enough there was a speed trap. I really don't like driving by luck, if you know what I mean.

Is there something that is causing this? I do not recall that it has ever worked correctly, but I recently had another incidence of "luck" and decided to search this forum to see if there were any related posts. I didn't find anything via the search function, so I apologize if "LS460 Cruise Control" wasn't a specific enough search.

Thanks for any tips.

Tom

roadfrog

Automatic downshifting with cruise control on? hmmmm, wasn't aware that this was a thing? My 08 definately does not have it, but it will downshift when going downhill and I tap my brakes a few times.

SW17LS

It should downshift to hold your speed when going down a hill. A few MPH is acceptable but 10-15 MPH is certainly not right. My LS downshifts to hold speed using CC, as does every other Lexus product I've owned.

peteyx

From the little research I've done, it appears that only those Lexus with radar cruise control are equipped with ACC, which will downshift to maintain speed.

SW17LS

That is incorrect. I have never owned a Lexus with ACC and my Lexus vehicles will always downshift to hold speed. I've taken many long highway trips in the mountains of WV in my Lexus vehicles. It won't take extraordinary measures if it's a really steep grade, but they will downshift. If it's a long 7%+ grade you're going to need to downshift yourself to lower gears than it will go on its own to avoid riding the brakes.

Only Lexus vehicles with ACC will apply the brakes, but they all should downshift.

tcarroll2

So, is there be anything I can do to fix this? I was wondering if maybe it is a vacuum issue, but that doesn't make any sense because I doubt the cruise is connected to vacuum. Possibly a bad sensor somewhere?

SW17LS

What sorts of hills are you riding down on when this happens? Watch the tachometer, does it downshift at all?

Like I said it will downshift to a point, but if it's a long steep downgrade (7% Etc) it won't downshift enough to hold its speed. But it should downshift and try.

peteyx

My first Lexus was a 1991 LS400. I just sold a 2004 LS430. Neither of them would downshift to maintain speed. When I take delivery of my new-to-me '07 LS460, I'll see if that one will downshift.

SW17LS

My 2004 LS would downshift to hold speed...as did my 98 LS, my 03 ES, my 10 ES and my 13 GS. As does my 15 LS. The GS was actually annoying because it would rock back and forth from 6th to 5th and would feel like it was bucking, its well documented in the 4GS forum.

Its not going to downshift to third gear, but if you watch the tachometer, it will come off of its cruising gear and use engine braking to slow the vehicle down. If its a long steep highway grade then yeah, its going to require you to manually downshift.

In all the highway traveling I've done in my Lexus cars there is only one hill that requires me to downshift to use engine braking to slow the car down on a downgrade, coming down Sandstone Mountain on I-64 eastbound in WV. About halfway down the grade the momentum is too much for the cruise control to maintain the speed. Haven't taken my 15 LS on that trip yet, but that was the case with all my other cars.

7milesout

I'm guessing the 2007's to 2009's are just not programmed for it, from the sounds of things. My 2010 does this on radar cruise or normal cruise. I would wish it would not, I'd rather it rollout and pick up speed. I look ahead and can watch for the heat.

SW17LS

I highly doubt that. More likely it is downshifting and the drivers just aren't realizing that its doing that.

7milesout

I wouldn't think so, if it's picking up like 15 mph. Mine will shift down multiple times. It's VERY noticeable. If I think it's going to do it, I will cancel the cruise and let it roll. Then resume when it gets near the set speed again.

There's a couple of assumptions on my part driving like that. 1) I rarely go much more than 5 over the speed limit, so letting it roll even faster is not all that risky for me, and 2) I assume that most LEO's are not horse's behinds (sure some are), and therefore I assume they would find a place that is more legitimate to measure a person's speed than an area possible affected by gravity. If I were a LEO, I would choose a level area (if possible) to judge a person's speed. If they're speeding there, then I would stick it to 'em.

I rarely go more than 5 mph over the speed limit because 3 main reasons: 1) It's a big stress reliever to not have to even consider watching out for the heat. 2) If I'm not gaining on people, they don't get on my nerves by NOT getting out of the fast lane (so less chance to get frustrated behind the wheel). And 3) I am just too darn CHEAP to consider the possibility of giving the gobment additional money (from fines) for them to waste, or to give insurance companies higher premiums, or to pay more to burn any more fuel than I must.


7milesout

SW17LS

Thats the ACC, it will also apply the brakes. The standard cruise control won't go to that level, but it will downshift once to try and hold the speed.

jmcraney

The way this works is dependent on how your vehicle is equipped and your driving mode selection.
Some vehicles have a "Paddle Shifter." And depending on whether it has the paddle shifter, the modes are D, S and M. So, I think to add clarity to this discussion, everyone needs to say how their car is equipped and the driving mode they are referring to. I think the Econo selection also impacts this. And I think some people don't know what mode they drive in - they just move the shifter until it "goes."

7milesout

Interesting - Mine doesn't have the paddle shifters. But I wonder if changing modes (on mine) would change it from downshifting. A large portion of the time I drive with it in ECO mode. I'll switch it up and check this sometime.