Why is my transmission shifting down to third on hills while on cruise control when it never used to?

after having replace sensors with new items ( not 2nd hand units ) and the codes reappear then the problem was not fixed by the sensor replacement. IN the list of possible causes for the codes ,the TCM will be a prominent failure point and the wiring and connects are next. Down the list will be mechanical failure and this need to be checked out by a pressure test being done on the transmission, adjustments to the band and clutch packs. Check all wire connections for clean pins and tight connections . The cruise controls requires a constant circuit for it to work so that any failure of a circuit indicates the need for the driver to resume control of the vehicle ( braking-)

the cruise control limits have been exceeded
the rad speed drops going up hill, the transmission shifts , that exceeds the rpm so it drops back the gear s shift again and the cycle is repeated
nothing really wrong , just incorrect driving practice
good practice is to turn of the cruise control when going up hills that puts the control outside parameters for the operation

check the rpm and road speed when this happens . The cruise control will increase to keep RPM constant but as the road speed drops the auto may be shifting down and as the rpm increase it shifts back before the rpm adjusts. You can override a cruise control in this situation by simply pressing down on the accelerator to maintain the power setting and road speed and when the situation is passed and you take your foot of the accelerator the cruise control will return the system to the set position without you needing to do anything

maybe start with the fuel filter or pump. possible screen collapsed or plugged.

Since this should still be under factory warranty I would check with the dealer first. Could need to have the computer re-programmed.

There is a cable that goes from your throttle body to the transmission.This is called the throttle valve adjuster cable.It has either come out of adjustment or is bad.You need to go to someone that knows how to adjust this and your problem should go away.There is a special adjustment procedure so you can`t just move it to where ever you want.This controls when you vehicle will up shift or down shift depending on the input from the gas pedal.So have someone that knows transmissions help you or take it to a reputable shop and get it fixed.It is not that big of a job.Hope this helps.Good luck.

It could be your transmission trying to find the right gear it will jump around on diffrent road surfaces and going up hills/down hills. It is usaully noticable on cruise because it is at a constant speed and your thinking why would it need to shift. Sometimes it doesnt even really shift the gear its so inbetween it just jumps back really fast.

do a code search check codes on yahoo also go to youtube and finde code search vid

Simple answer, no, it will not most likely cause any increased wear to your engine or transmission. Yes, it is normal for the engine to rev while climbing a hill while in cruise control.

The cruise is designed to be used on flat (or semi-flat) stretches of highway at 55mph or higher so you don't have to hold the fuel pedal the whole time and your foot doesn't get tired. The cruise control system will try it's best to keep your vehicle rolling at the set speed, increasing/decreasing the throttle to compensate for changes in engine load.

If you are driving with cruise on, try lightly putting your foot on the pedal and you might notice that the system will actually move the pedal itself. If you are in cruise, and you come up to a large hill, try putting your foot on the pedal and getting it up the hill on your own w/o cruise then resetting cruise once you are off the hill.

Also, cruise is not supposed to be used in moderate/ thick traffic or on country roads with a lot of rolling hills. The cruise control system is a "dumb" system meaning (not that it's pointless) but it will only change the pedal as the speed changes and it has no idea what's coming up next, even while you are already on the hill.

So, it is normal operation of the cruise control to try to compensate for a hill by constantly revving up the engine and letting it fall back down to try to keep moving at the exact same speed you set it for. If this is a bother, you can always use your foot to hold the pedal while climbing the hill normally.

Don't worry, it won't cause any increased wear and tear on your vehicle. I hope this helps. Good luck and don't forget to rate! Thank you!

have you had the transmission flushed? it seems to be caught in a limbo. where the calibration of the speedo and the transmission are not compatable. Now as wierd as that seems it happens usally like when going up a hill if you have a manual trans. and cruise locked in. it cant hold that speed and moves to a different speed if you dont down shift. Or perhaps your cruise control cable is slipping. is it vacume over mechanical? pop the hood and make sure all your hoses to cruise control are tight and no leaks.