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Toyotapro, ASE master tech
Category: Toyota
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Experience:  ASE Certified, 10+ years Lexus and Toyota Certified
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Toyota: cruise control..going uphill..higher speed..the hill

Resolved Question:

I have Toyota Highlander.
There is a cruise control problem.
When going uphill the vehicle instead of
running at set speed (let us say 70 m/h) it is going with much higher speed. The steeper the hill the higher speed difference between set and actual speed. Sometimes when heel is very steep the actual speed is higher than 75-76 m/h, while the set speed is 70 m/h. It retuns to normal speed when go on even road.
Is it abnormal? Can it be repaired? I'd rather would like to have 64 -65 m/h at described situation.
I would like to emphasize this happened when you go uphill not downhill.
Submitted: 5 years ago.
Category: Toyota
Expert:  Toyotapro replied 5 years ago.
Hello and thank you for using just answer! Most commonly this is caused by the vehicle needing to downshift to maintain power and speed. Yes the condition you experience is "normal" but can be avoided by simply shifting the vehicle out of overdrive on hills.
Customer: replied 5 years ago.

I am sorry, but what you told I have already known. The main question was at what speed difference it should be considered abnormal: 76, 78, 80, 82, 84, 86, 88, 90 ???

I do not think that 75-76 m/h is normal. I have another toyota vehicle - Solara - it does not have this problem

Expert:  Toyotapro replied 5 years ago.
There is a 5mph speed tolerance built into the cruise logic. Under light load the car will usually maintain the EXACT speed you set it at but down big hills or up big hills/grades this can can confuse the system, ESPECIALLY lets say for example if you were towing a trailer. The solara while yes it is a toyota it has a completely different powertrain, is a much lighter vehicle and does NOT operate the same so it cannot be used for an apples to apples comparision. If you question weither this is "normal" or not what i would recommend you do is drive another one from the dealers lot with the same engine and compare it. The only thing that can be altered or changed in the computer system is by going in with the dealers scan tool and doing a "memory reset" on the ECU logic, this usually only needs to be done however on a vehicle that establishes really weird memory or if for example the computer is reflashed or a major repair is performed. Sorry for not getting back to you sooner, it has been a crazy busy day in the shop and I was not able to get back online.

Customer: replied 5 years ago.
So, if it is more than 5mph I can ask them to repair the cruise control system? It is still under warranty.
Expert:  Toyotapro replied 5 years ago.
If you have more then a 5mph variation then you need to ask them to do a master memory reset yes.
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