H3 Cruise Won't Stay On, Bucking While Slowing

[arcwcb]

So while driving home today, I noticed that my cruise control would turn off after 15ish miles, but I could turn it right back on and it would be fine. Then, as the trip went on, the distance kept getting less and less (down to maybe 3-5miles between turning it on and it going off on it's own). Also, during this time, I noticed that sometimes while slowing down for a stoplight, the vehicle seemed to "buck" or pulse while slowing down to a stop, related to speed (as I got slower, the bucking slowed proportionately, intensity was the same though). Other times it was smooth. At one point, the speedo even randomly dropped 15-20mph then bounced back up to the speed I was going, and another few times got a little jumpy and then smoothed back out.

Any idea where to even start with this?!?

 

[4speedfunk]

Check your battery and main cables first.
The speedo bouncing points to a failing VSS, which would also disengage the cruise control. A faulty brake light switch (at the pedal) can also exhibit the same symptoms. Scanning the codes can point you in the right direction, and keep you from throwing hundreds of dollars at it.
Also check the VSS harness for rodent chew marks.

 

[arcwcb]

Battery is good (~1 year old) and the cables are good and tight, no insulation damage. I was reading other threads and I thought it may be the VSS. I don't have a check engine light or anything, will it still register fault codes without setting off the light?

 

[JPaul]

Battery is good (~1 year old) and the cables are good and tight, no insulation damage. I was reading other threads and I thought it may be the VSS. I don't have a check engine light or anything, will it still register fault codes without setting off the light?

There might be pending codes you can pull with a scan tool. The computer will set those if there was a temporary issue but hasn't become a constant problem yet. Engine misfire is one type of code that can be a pending code, I have one myself from my drive back home from Moab last night.

If you don't have a scan tool go to autozone or somewhere and they can check for you.

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