A user reported this symptom with their cruise control: Has anyone else seen this symptom? This is not the Woz problem of incrementing and decrementing speed and having a delayed application of these change requests at one time. RECOMMENDATION If possible, perhaps you could drive to a dealer service center with the problem and keep them from turning off the car. Have their service technician or staff confirm the problem. In theory, they should be able to plug in their diagnostic system and capture 'live data' from the problem. The cruise control consists of: set of resistors in series within the stalk assembly stalk switches that tap different parts of the resistor network wiring harness control computer line that reads the resistance values If I were trying to diagnose the problem, the first step would be to read the resistor network values and look for noisy contacts. If the values are marginal, swap the stalk. But having the problem clear by power-cycling the car points towards the control computer. All I can do is suggest that every time it fails, write your notes including as many environmental conditions as possible (aka., time, weather, miles or time before failure, internal temperature setting) and when you get back, make a service call at the dealer. This also establishes a rate. What this does is make a formal log so the dealer has backup to justify 'parts swapping' and escalation. Eventually, it becomes time to escalate the problem to their next service level. It is a negotiable point to work with the dealer. It would be nice if we could move this sub-discussion to Maintenance. Bob Wilson
I have had an issue where the cruise is set, and I use the gas pedal to accelerate temporarily, then when I lift off it's like the cruise forgets where it was set and just drops down way below where it had been - even though the "set" light is still on. Also (maybe this is by design), whenever I shut off the car, the cruise switches off - next time I start, it has to be turned on again. annoying.
I may have seen that but I need to retest. If the car drops below 23 mph, it forgets all settings. I wish it would go as low as 10 mph for some of my engineering studies. Bob Wilson
Happened to me last night. I have owned my 2010 Prius for two days and it wouldn't engage the cruise control. However, when i restarted this morning, the symptom was gone and all was well. Have you found a solution yet?
All cars that I have owned did that, any change in speed, acceleration or braking would turn off the Cruise Control even if the light still said set. A Blazer, Optima and the Prius. I thought that was just how it was...
Thanks to the suggestion from vday, I determined that if I had downshifted using 'B', the Prius stays in 'B' even though it operates normally and you thinkyou're in 'D'. So, simply popping the gear back to 'D' worked and I was able to engage Cruise Control.
