Coming back from Las Vegas to California, I had the cruise control set on the speed limit going up a hill. Half way up, the cruise control dropped as did my speed from 70 to 56. There were no warning lights but the battery meter was in the one bar pink range. I managed to continue up the hill at 56 mph by flooring the accelerator. When I got to the top and started to regenerate power to the battery, I regained power and speed. I am discussing a 2008 Prius with 89k miles. Any ideas as to what the issue may be ( like battery pack declining efficiency)?
This is completely normal. You probably went through that 3 times on your way back to Los Angeles, at every Hill you climbed. SM-N900P ?
konamonk, You have to consider the age of your battery pack and the amount of cycles on the pack. As with all batteries they tend to weaken over time. What you are experiencing is related to the pack weakening. As JC said, it is normal. Does this mean the battery is toast? Absolutely NOT. Until the dash lights up, just try to drive conservatively to maximize the life left in your battery pack. If and or when the pack does code out then you can either fix it yourself, get a newer one out of a wrecked Prius, get a rebuilt from someone like Dorman, or lastly get a new one from Toyota. Those choices and decisions can be made at that time. Heck, you might get a hankering for a Gen III or even the upcoming Gen IV. I had a perfectly good Gen II, one day I just went and bought a brand new Gen III. I liked the Gen II. I love the Gen III. Ron (dorunron)
That (holding high speed on hills) does seem to be a fairly common issue, and yeah I think it does get worse as the traction battery ages. TBH you're better off driving larger hills without cruise control, and just letting the speed naturally drop back a little bit on the steepest parts. BTW. Just to rule out any more serious issues, did your cruise control functionality return almost immediately after the event, or did CC stay out of action for some time. If the inverter coolant pump goes out (or the inverter overheats for any other reason) then CC does go out of action until it cools. So you might want to get that checked out.
I make this trip quite a few times a year and as I recall my CC has never just quit. If I'm carrying a heavy load uphill, I can see the speed dropping and I normally switch off the CC and take it manually up the hill. But I can't remember ever having the CC quit on it's own without me disengaging it. Uart might be on to something.............
As soon as I got to the crest of the hill and generated a new bar on the battery meter, all power and function returned.
Speed continued to drop until CC disengaged on its own. I could only maintain about 56 in speed flooring it. As I got to the crest of the hill and started to regenerate the battery, all returned to normal. The battery indicator ranged from green to purple on a few other hills but it never dropped to 1 bar as I backed off of speed and tried to keep it charging. BTY - on the way out, I fought sever head winds and hills for miles on CC with no issue. This was the first time it occurred.
Have you checked your fluid levels recently? Oil and coolant? If the car is not getting enough oil or coolant, it can have a tough time producing power. During the long uphill climb you are only using that little 76 hp engine. It's not all that great. If your AC is blasting, it will also make it worse. I don't think there's anything wrong with your car, I've experienced it many times. I did however see a lot of improvement once I changed my spark plugs. Maybe you can try that too.
Have you removed and inspected the engine air filter recently? If not, remove the filter and hold it up to sunlight. If you don't see light coming through the filter element, replace the filter. When I lived in south OC, I made the trip to Las Vegas on I-15 numerous times in either the 2004 or 2007 Prius, and did not ever have trouble maintaining the speed limit + 5. Similar experience driving on I-5 north out of Los Angeles up the Grapevine. So I would not be quick to say that the Prius not being able to maintain the legal speed limit is "normal" behavior.
It was the first time that happened to me in 7 years so I do not place the experience in the "normal" category. I had replacement air filter to be used for the upcoming 90k service. I replaced it as the other was dirty. Thanks for the response.
Will you have a chance to test your car's performance at high speeds in mountainous terrain, in the near future?
I haven't had the chance to try cruise on hills yet with my Prius C but this used to happen with my previous gas powered cars with the exception of one that has a turbo and the other supercharged. Both those kept the cruise spot on no matter the hill angle but every other one lost enough speed that the cruise cut out - finally found in those car manuals that was a normal happening.
2006 Prius losing power on Hills | Page 2 | PriusChat I also posted with this same problem. It was the VVT Oil Control Valve. Replaced it and I now have power, stronger battery, no codes, and it worked. See my post with more details. .
I just fixed the same problems after years of no power, lost MPG, low battery SOC at high speed, occasionally a code P0011 by replacing the VVT "Oil Control Valve". It is like night and day and my Prius is running like new.
