Cruise control losing speed

That is normal for that year models, I think. Earlier cruise control just maintains the engine RPM in relation to speed. It does not use auto braking to reduce downhill speeds. Best way is to get it scanned with diagnostic scanner that can reset or check error codes for cruise control.

Which engine ?
Cruise Control Description and Operation (3.6L)
Cruise Control Description and Operation (3.4L)

Do you know what all is involved in C.C. operation ?


Cruise control is a speed control system that maintains a desired vehicle speed under normal driving conditions at speeds above 40km/h (25 mph). However, steep grades may cause variations in the selected speeds. The main components of the cruise control system are:
• The cruise control module assembly
• The cruise control switches
• The cruise control release switch
• The powertrain control module (PCM)
• The stoplamp switch assembly
• The vehicle speed sensor


The cruise control module controls the operation of the cruise control system. The cruise control module monitors the signal circuits of the cruise control switches. When the normally open cruise On/Off switch closes with a switch activation, the cruise control modules detects a high voltage on the signal circuit. The cruise control module activates the cruise control system.The set/coast switch and the resume/accel switch will not operate the system when the cruise control module has not activated the system based on the cruise control on/off switch signal circuit .
The cruise control module monitors the cruise control set/coast switch in order to determine when to capture and maintain the vehicle speed. The cruise control module monitors the vehicle speed signal circuit in order to determine the desired speed. The PCM pulses the vehicle speed signal circuit at 4000 pulses per minute. After an initial set speed has been established, the cruise control module also uses the cruise control set/coast switch signal circuit in order to tap down the set speed when the cruise control module detects a switch activation.
The cruise control module monitors the cruise control resume/accel switch signal circuit in order to determine when to resume the previous set speed. This feature only works within the same ignition cycle and as long as the cruise wasn't turned off using the cruise control On/Off switch since the last cruise engagement. After the set speed has been resumed, the cruise control module also uses the cruise control resume/accel switch signal circuit in order to tap up the set speed when the cruise control module detects a switch activation.
The cruise control module assembly has a controller and an electric stepper motor to vary the throttle in each different cruise control mode. Two components in the module assembly help to do this. The electronic controller and the electric stepper motor. The controller monitors vehicle speed and operates the stepper motor. The stepper motor operates in response to the controller, to maintain the desired cruise speed. The electric stepper motor moves a strap that is attached to the cruise control cable which moves the throttle

Are you on a flat road when this happens, if so it is not normal, if you are climbing it is normal because this car is underpowered for that and the cruise will lose speed, have first hand experience with this .

Check the linkage at the advance to se if it is broken. Some are by mechanical connection and others are by vacuum. If vacuum you have developed a leak and must replace the controler to make it work again.

try replacing the brake switch.

go to junk yard and get ecm and change out

If the cruise control actuator is vacuum controled I would be looking at a problem with the rubber hose.--cracxked , broken or hard and not sealing.. Cruise controls normally work with a less then 150rpm variation and respond when that setting is reached. Check that the cable is correctly adjusted of if cpu controlled that there is not a fault code reading

First I'll assume you haven't read the owners Manuel, Cruise control is not perfect on any vehicle. if coming to a hill put foot on gas to help rpm, going down hill put foot on brake to keep same speed, cruise control operates off of engine vacuum. Speed sensors can be affected by putting on smaller or bigger tires than what is on drivers door.

I just bought a 2011 Sonata and am experiencing the same problem. Going downhill with cruise set at 55 mph; speed increased to 70 mph and was still accelerating (from the downhilll grade) when I finally pressed on the brake.
This is not normal. My Honda Accord never varied from the cruise setting by more than 3 or 4 mph ... going uphill or downhill.

My experience is that cruise control works on level roads, uphill you have to control speed yourself same for downhill. Exception is very powerful cars. Did it maintain speeds before? (uphill + downhill)