I have had trouble with the cruise control on my 2012 Hyundai Sonata Limited since I bought it last November. The dealership had engineers from Hyundai come in and help them out with the first problem, but now a new problem-- a really dangerous one- has come up.
When I hit cruise control going downhill at anywhere between 55 and 70 mph, the rate of speed increases as the hill gets steeper. This is a new issue for this car. I drove it with one of the service techs in the car with me and it did what I mentioned above. Then I had him drive it. Same deal. He claims that he used to install cruise controls into cars, and that this is normal. I have driven many other cars in my life, and never experienced this.
Is it possible that he is telling me the truth? I have one more appointment at this dealership. Hopefully the next tech will take me seriously and try to fix the problem, but I know how people talk, and I don’t have a good feeling about this.
So, I would like to know if anyone else has had this problem with a new-ish Hyundai or any other car. I would also appreciate ideas about what this guy is saying to me and how to proceed if this dealership hangs tight to the assertion that this is “normal”.
Gee, that is a bit odd. I was on a roller coaster at Cedar Point this past summer, and the steeper the dang hills would get, the faster that train would go!
Seriously, I don’t know how steep you’re talking here, but cruise control systems don’t apply the brakes, and 2012 cars have 5 and six-speed automatics with very tall gears, along with very low-drag body designs. You may just have to hit the brakes here and there.
Agree with Doubleclutch. First why would you engage cruise going down hill? It really is more intended for leveler areas to maintain speed. All cruise does is adjust the throttle up or down according to the speed it is seeing. Going down hill, all it can do is let up on the throttle completely and if that isn’t enough to slow the car, it’ll coast faster. Might want to just re-read the section on cruise in the owners manual and it’ll explain it a little more. But it really shouldn’t be used in hilly areas, short trips, low speed etc.
The throttle plate on this vehicle is, I believe, controlled by a signal from the gas pedal through the ECU driving a motor to operate the plate, nulled by feedback from the throttle position sensor and, when cruise control is engaged, modified when your speed begins to drop by a signal from the vehicle speed sensor. In short, when you engage the cruise control, the throttle motor signal should null to the setting it’s on when the CC is engaged rather than to the gas pedal signal. The attached illustrations should help provide some insight.
First, as others have said, the CC will not slow you, only accelerate you.
Second, there may be a fault codes stored in the ECU. The ECU does have the ability to detect cruise control problems and point a tech in the right directionn
Finally, the shop may have to put a recorder in the system and record the accelerator pedal signal, the cruise control module signal, the throttle motor signal, the throttle position signal, and the vehicle speed sensor signal while the vehicle is exhibiting the condition described. That would be an absolutely definitive diagnostic step.
Oh, and as always, manufacturer’s technical srevice bulletins(TSBs) should be reviewed. There may already be a fix for the problem. Perhaps some reflash of the ECU map or something.
Having said all that, make sure all the info is recorded on the shop orders when you bring it in, keep your copies as evidence, and check into your state’s Lemon Laws, just in case. A complaint to NHTSA wouldn;t hurt either.
You are not getting the runaround from your dealer. You just don’t want to accept the truth. This “trouble” is normal in all vehicles without “adaptive cruise control” which is an expensive option. Your standard cruise control is working normally whether you want to believe it or not. Read your owners manual. Cruise control is not designed for going downhill in the first place. That’s why you have brakes.
Missileman, you might be right, but i don;t think we have enough information to know that yet. I’ll take the OP at her word that the vheicle is acting differently than it used to. She could well be getting an unwanted signal from the TPS or the accelerator pedal module.
Ospina–You can count me as one more forum member who wonders why you would decide to engage the cruise control when going downhill.
The garden-variety cruise controls that have been standard equipment on cars for the past 20 years or so DO NOT apply the brakes. Without that capability…How could cruise control slow your car on a downgrade? Yes, the very expensive “adaptive” cruise control that is optional on some cars can slow your car, but standard equipment type of cruise control cannot do that.
Cruise control is essentially for maintaining a steady speed on flat surfaces. When you encounter an uphill grade, the transmission will frequently downshift in order to help maintain speed, and the throttle will frequently open more widely in order to help maintain speed. But, when you come to a downgrade, you do need to use your brakes if you want to avoid going too fast.
And, just for future reference, you should not use your cruise control when driving in the rain, or on wintery surfaces. During these periods of reduced traction, you want to control the speed yourself, in order to reduce the chance of hydroplaning and skidding. All of this should be covered in your Owner’s Manual.
I use cruise control on steep hills, not a lot, but have found it useful for long irregular downhill/uphill stretches of highway in the mountains. Going downhill the car speeds up a few MPH but not more than that. On particularly steep downhill grades the transmission downshifts. My cruise control also has a coast function. It will allow the car to accelerate beyond the set point.
The OP has a right to be concerned if there has been a dramatic change in the way her cruise control functions. The dealer has an obligation to explain.
We have come to depend so much on computer systems to protect our safety and health there is a tendency to forget it isn’t the computer, but the software engineer and programmer who make the decisions on our behalf. Even with rigorous testing mistakes are made.
You’ll want to check me on this, but I know that Hyundai has recently put out a recall for newer Sonatas. It may be for 2013s, rather than 2012s - and the recall may have NOTHING to do with the cruise control.
Some vehicles have a hill-sensing transmission, which will downshift when it detects acceleration coupled with a idle throttle input.
It would not surprise me if Hyundais do not have this feature - They make, now, very good cars, but they still sell very inexpensively compared to the competition. They have to cut somewhere, and esoteric features that most people don’t notice tend to be one of those areas.
In short, it is entirely normal for a vehicle to accelerate at idle when it’s going downhill.
It is only a safety issue if you, the driver, choose to stop paying attention to your driving in the belief that cruise control should handle it for you. This is a habit you shouldn’t get into even in Google’s self-driving cars. Cruise control does not override the brakes (the opposite is, in fact, true), and so when you see that you are accelerating when you don’t want to, you should use the brake pedal and eliminate the “safety risk.”
Thanks for all of your comments. I would like to say that I use CC on hills when I am making long drives where there are hills
My guess from this discussion is that Shadowfax makes a good point when saying that Hyundai has to cut somewhere.
It still boggles my mind to consider that every other car I have ever driven - some old, some very new, maintain a steady speed on these same hills I drive – and yet the general consensus here is that this NEW behavior in the Hyundai is normal. I live in an area with hills. Why would I want to drive for 4 hours with this kind of cc?
I use CC on hills as well. My MR2 accelerates going down a steep enough hill (the top gear in it isn’t very tall, so minor hills are enough for engine braking to take over). My TL has the hill-sensing transmission, although even with that it still accelerates if the hill is steep enough. I cannot drive down from a mountain pass in the TL on cruise control without it accelerating.
I stop short of recommending that you not use cruise control on hills - just that using cruise control does not make looking at the speedometer unnecessary.
BTW, older cars with vacuum cruise controls were even worse. They’d lose speed up hill and barrel down hill.
Without actually driving your car, I can’t comment as to why it is “suddenly” accelerating down hills when it never did before. I would suggest, however, that it is possible that it has always done this, and you are only now noticing it because of the extra scrutiny you’re giving cruise control after the last repair (and since you never told us what the first problem is, we can’t really speculate as to whether or not your cruise control is truly broken). It is also possible that whatever was wrong with your last cruise control is what made it go slower on hills - off the top of my head, if the last cruise control was sending wonky throttle inputs, the transmission might not have shifted into the highest gear, if it thought the throttle was being rapidly moved between closed and wide open. In a lower gear, your car would naturally slow on downhills, at which point the cruise would open the throttle a bit to maintain speed.
Before I jump in and disagree with all the advice given, you should try this test. When you feel the CC is allowing the car to speed up when going down a hill, with your foot off the gas, reach up and turn off the cruise control button. If you feel a sudden deceleration right after you turn off the cruise control, then all previous advice given here is null and void, you have a valid problem with your cruise control.
If this test shows that you do have a valid problem, then repeat it for the dealer and let them know they have to fix it or you will be reporting it to NHTSA.
I had one car that would always bump the speed up 1-2 mph when I engaged the cruise. No other car I’ve owned did this, but this one did. Going downhill and engaging the cruise in that car would result in a greater than 2 mph bump, more like 3 to 5. That could be disturbing.
I’d advise only engaging the cruise when you are on flat or an incline in the road. With the high final gear ratios to get mpg, and if the auto transmission provides little engine braking your car can pick up significant speeds above the setting on the cruise on downhill slopes. If you want to use cruise you might be able to shift to a lower gear or turn off the overdrive on the downslopes.
You never explained, what was the first problem they worked on it for? This might help understand if it’s possible the prior work could have contributed to the difference you’re noticing.
Secondly, why don’t you take a similar car from the dealer on a test drive. How it reacts could determine how you should…
this not a tractor-trailer where the speed control will work with the “Jake” brake our engine brake if the truck gets going to fast about 5 to 10 mph over set speed. if my car is on the speed control and to keep it under control i downshift it from OD to “3” and that helps to control the speed goind down a grade with out having to oveer use my brakes.
For anyone who is interested, I took a 2013 Hyundai Sonata for a test drive and had the same issue with hills. Thank you, TwinTurbo. Originally I had brought it in because I would press cc; sometimes it would work, sometimes it would not. It took the dealership 3 tries (they could never duplicate the problem) and a consultation with Hyundai engineers to fix that problem.
Two months went by with the cc working as I expected it to ( even on hills). Then one day, it just changed, and the cc did not work going down hill, which apparently means that when it was working as my Honda had on hills, it was broken, but now it is “fine”. We shall see what the next long drive through the mountains brings…
