2008, GLS, 4 cyl with 30K miles.
The cruise works great as long as the road is fairly even. But when some hills are involved, like just regular hills that are a couple of blocks long, I'm in Minnesota so there are no big hills, the cruise picks up speed. As soon as it senses the car is slowing down due to the hill, it accelerates until it reaches the top of the hill. So if I'm going 60, by the time I'm cresting, I could be going 64 or 65. I don't know just how fast it would go if the hills were steeper or longer. It does level out once the road levels out. But, what can I do about it? I don't want to get a ticket because of the stupid cruise control and I hate the idea of shutting it off going up every hill. I've talked to two dealers and they both say there's nothing that can be done about it. They said it was because the engine was under powered, it was unable to compensate correctly. I've had engines with far less power compinsate just fine so I don't buy that. Anybody else had this experience?

 

Here's what the TSB says:

This bulletin updates TSB# 02-40-018 to correct operational information.
DESCRIPTION:

The cruise control module for vehicles equipped with automatic transaxles is designed to prevent "busy shifting" (frequent downshifting and upshifting) when driving in hilly terrain. For this reason, the cruise control module has the following internal logic:

· If the vehicle speed decreases more than 4 mph below the set speed, the cruise control module will:

*
Command a 4-3 downshift (5-4 downshift for XG300/350)
*
Hold 3rd gear (4th gear for XG300/350) for 20 seconds before allowing an upshift (even after cresting a hill)
NOTE
The Santa Fe cruise control module will not command a 4-3 downshift above approximately 73 mph.

The cruise control module will disengage cruise control:

*
If vehicle speed is below 25 mph
*
If "Sports Mode" is engaged (XG300/350 only)
*
If the brake pedal is depressed
*
If the gear shift lever is moved to the "N" position while driving
*
If the vehicle speed drops 10 mph below the set speed
*
If the clutch pedal is depressed (manual transaxle only)

If a customer comments about the cruise control operation, please explain the above information to the customer.

 

Good info, Jsinton!

That explains all my questions regarding the cruise control option.

Thanks!!

 

I appreciate the information. However, the hills I'm having experience with are relatively shallow hills. They, in no way, even come close to needed to down shift to keep up. My little KIA holds just fine going up and down with barely noticeable change in rpm, according to my Scan Gage it changes about 200 rpm. I haven't put the Scan Gage on the Sonata. Actually, if it wasn't for the speeding up, the Sonata's rpms would change close to none. So I don't think that this would play into my situation. Would it? Maybe I'm misunderstanding the TSB.

 

This explains the down shift I had today while driving over an overpass on the highway in Florida. I was doing 60 MPH and on cruise control for a couple of miles and I felt it accelerate but it wouldn't change gears. It just got stuck at 4,000 RPMs. I went over and down the other side and it still wouldn't shift. I just turned off the cruise control the car shifted and I kept on driving. I set the cruise control and everything worked without issues.

I can't imagine waiting 20 seconds for the system to adjust. There goes all my fuel economy!

I am driving a 2010 Hyundai Elantra Touring GLS. 3,200 miles in 30 days and this is a first.