Touchy cruise control

#1
has anyone had the issue with the 2018 Corolla where the cruise control will overshoot it’s set point while descending a hill and then downshift the time transmission causing the engine to rev up to 4000-5000+ rpms to slow the car back to set point
 

jolly

New Member
#2
Seen a few on forums. Is it on regular cruise or radar cruise when it happens. The latter is only program to work on flat road.
 
#3
Seen a few on forums. Is it on regular cruise or radar cruise when it happens. The latter is only program to work on flat road.
My 2018 se only has radar cruise and that always happens when going down a hill. Radar cruise is recomended on all roads that are not slippery ( snow, ice, rain )
 
#5
it just seems they use the cvt to do more of the "downshifting" to slow the car down over the brakes sometimes when going downhill on cruise... then seems like the fuel pressure goes up when going up hill to keep up with the cruise speed then when you plane out that pressure kinda boost ya up 5 to 10 mph above set cruise and the cruise doesnt give a fck so it wont slow you down for awhile.... thats really been my only draw back with my corolla... the cruise is tricky, i find it best on auto mode over the manual mode.... but the manual mode i can kinda control the "shift" points when going up or downhill....
 
#6
Radar cruise is recomended on all roads that are not slippery ( snow, ice, rain )
You only have regular cruise or radar cruise not both !
No. Check your manual. You have 2 modes, specifically because Radar CC doesn't work well in every conditions (the list is half a page, including downhill beside ice rain and snow).
-Press "ON" : Vehicle-to-vehicle distance control mode (Radar CC). You can adjust the distance to respect.
-Press "ON" and hold for 2 seconds : Constant speed control mode (Régular CC)
 
#7
I'm running into the same basic issue with the cruise, revving up to 3.5k to 4.5k. This happens most often at 60mph, and happens less often at other speeds.

When I notice it, tapping the gas peddle makes it go away.

I have no idea why tapping the gas makes it go away instead of making it worse. If the revving has anything to do with slowing the car down then tapping the gas would only create a situation where the car would need to slow down even more, but that's not the case.

The high revving isn't slowing down the speed that the car travels, it just uses more gas to go the same speed.

I called Toyota and had to talk to 3 people before someone would listen.

I'm convinced that Toyota needs to update the firmware in order to fix this issue. The question is, will they? I hope so, but I'm not betting on it.
 
#9
My radar cruse control does the same thing. I believe the high revs are more related too a software problem with the radar cruse system. The reson I say this is it doesn’t happen with regular cruse control, the RPMS stay as you’d expect. If it was a problem with the transmission then it would rev high using both cruse systems. I I believe the firmware/software update earlier this year was supposed too correct the problem but when Toyota realized the update didn’t work the update was canceled. So at this point it’s a Waite and see.
 
#11
Radar CC doesn't work well in every conditions (the list is half a page, including downhill beside ice rain and snow).
I read that list and decided that Radar CC isn't for me. It's easier for me to just keep the speed where I want it myself, than to be on alert for all those different conditions. There sure are a lot of them.
 
#12
I got the firmware update for the CVT recall/service thing. I can confirm that the cruise control still revs high when going down a hill, even with adaptive CC disabled. I’m thinking the ECU might be trying to downshift, but cannot since it’s a CVT, so it just ends up reving high.
 
#13
I ran some tests, and the high revving when using the cruise is not engine braking. When the car need to slow down, it uses the same system as the brake assist, meaning the car actually applies force to the brakes pads, just like the brake peddle does.

The high revving actually happens on flat ground too, not just when going downhill.

I can confirm that the car goes faster downhill than it does uphill, and I assume that's to help increase gas mileage.
 
#14
People tend to use CC in situations that it's not really made for. There is some play in the speed controls going up hills and down. It's not really designed to use in places where there are hills. Most cars will accelerate going down hills with the CC on and use higher revs to slow the car after it reaches a higher speed. Best bet is to not use CC in the hills. What is happening is very normal though with CC on driving in the hills.
 
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