Have an 04 with 8500 miles on it with a weird CVT problem. In braking mode going down a long hill the engine RPM all of a sudden increases to red line (extremely high RPM). It has to be put into Neutral to settle it down. Mileage is down 25-30% as well. Dealer is calling Toyota Technical for assistance. The Prius Tech at the dealer told me not to put it into braking mode when going downhill. Problem is intermittant as well. Anyone heard of this before? I also have an 02 Prius with 48,000 and no problems whatsoever.
This is normal operation. Your battery is getting near full and the ICE must run to avoid over charging. Your tech should know that. You can continue to use B-mode going down hill.
efusco, The engine RPM is almost redline and would blow the engine if I don't shift to Neutral. It can't be because the battery is almost fully charged. It also happens sometimes just with the foot on the brake pedal going downhill, and not in braking mode.
Well, I'm not sure what to tell you....I think it's b/c the battery is at full charge and I know that the sound is not something you're used to hearing, but unless it is dramatically more than I think it is it is normal. They might be able to pull a peak RPM with the diagnostic tool or something, but I'm going to bet you they tell you that everything is normal. It is expected and actually supports my belief in a full battery and ICE peak rpm that it occurs in both B-mode and with manual braking. Check your energy screen next time it happens...I bet the SOC is in the green and either full or 1 bar short. This is a protective tool to prevent overcharge.
How would you know you are redlining? There's no RPM display. The car can sound like its reving more than a conventional car would. I would agree, check your energy flow display for SOC and what is driving what. B mode will tend to spin the engine unfueled, this is by design. B is for engine Braking, though it will increase regenerative braking until it has no more place to store it.
Since it is still under warrantee, the dealer should be willing to do a code scan for free, just in case this was recorded by the ECU.
Energy display shows all normal indications, and battery charge level is usually in the blue range. when it happens. Also stepping on the "gas pedal" settles down the rpm's as well. ECU shows no codes. Toyota told dealer to verify symptoms as they never heard of this problem. I know there is no tach in the vehicle but I have driven enough vehicles in my time to know when rpm's are very excessive. Also, my 02 Prius does not do the same thing on the same hills. I know the drive systems are different, but at this point the 02 Prius is getting better mileage than the 04. The 04 didn't exibit this behavior until recently. It is not temp or speed related either.
It really isn't. The engine is artifically restricted to a 5000 RPM limit. Many traditional systems allow you to climb pass 7000 RPM briefly without any problem. Also keep in mind that the Atkinson-Miller cycle sounds a little different than the traditional Otto and that the engine itself is closer to the firewall than usual (so it sounds louder).
While I may be proven wrong, the symptoms stated, and the actions taken to "settle down" the RPM, suggest there may be a problem with the electronic throttle control, specifically the pedal position sensor(s). I do not know if the Toyota system defaults high or low when the two sensors disagree, but by stating that things settle down when the throttle is changed suggests an open or short in the off throttle position with one of the sensors. This also could be the throttle actuator position converter. It sounds like the throttle is calling for or moving to WOT when the position should be idle.
That means you cannot draw a conclusion. Do what I do professionally (computer programmer) instead: identify behavior patterns (debug) Document each drive down the hill. That will hopefully reveal what's actually happening... Start charge-level. At what point all 8 bars are filled. How much longer between then and when the surging starts. When the charge-level drops to 7 bars. When the engine returns to normal operation. What the temperature is. What speed you are traveling at. Differences between "B" and "D" on that same drive.... etc. With enough data, a pattern will emerge. Then problem or design is much easier to determine.
Thanks to all who responded to my question. What bothers me is that this just started a couple of weeks ago. It didn't do it when I first picked up the car in August, and I drive the same roads and hills everyday. It is almost like a conventional car trying to go 40-50 mph in first gear. Toyota is going to try to duplicate the symptoms when I bring the car back to the dealer and the Svc. Mgr and I drive it down some hills. I'll let everyone know the results when we do that. It might be several days or a couple of weeks from now, but thanks again for the quick responses. As I stated before my 02 Prius does not exhibit the same symptoms at all and never has. Thanks again everyone, and I'll keep you posted when I have more info.
Please do keep us posted. It certainly isn't outside the realm of possibility that there is actually a problem and it would be good to share the information if, indeed, that is the case. I have a few more points, however, in light of what you just posted. 1)You'll notice that, in cold weather, there is a preference by the ECU to keep the battery SOC much higher than it tends to in warm weather...esp. when the vehicle (ICE &/or HV Battery) is cold. 2)B/C of that you may be noticing the issue of ICE reving more b/c the SOC before you begin your descent is higher, but he amount of regeneration is the same as it was in warm weather. 3)I still believe that this is normal operation and that you will come to believe that if you keep a closer eye on the SOC just before this situation commonly occurs. Similar 'symptoms' have been reported several times in the past and the high SOC was the cause. Good luck, and, for your sake, I hope I'm right.
Due to the general degradation and intermittant performance , it may be computer or TPS related problem. Sometimes the vehicle has power and sometimes it seems to struggle. Fuel consumption has gone from just around 50 mpg to 36.4 mpg (some of which I attribute to the cold weather, but not all of it). This AM I was stopped at a traffic light and the energy monitor showed my wheels moving and power flowing from the battery to the elec. motor and the motor driving the wheels, even though I was at a dead stop. I spoke with the dealer svc. mgr. just now and I am bringing it back in on the 26th. I'll let everyone know the results (providing they find the problem).
the 2k4 will show the wheels moving at a dead stop with light brake pedal pressure. The same pedal pressure in the classic Prius shows nothing. Just step a bit harder on the pedal and the wheels should stop turning on the MFD.
I did notice that and this morning pressed very hard on the brake pedal and it still showed movement while at a dead stop, and as a matter of fact, the display kept flipping between no movement and movement with very heavy pressure on the pedal. It's really acting weird. Also, the display seems to have a built in delay of 2 or 3 seconds between the gas or brake pedal activation and the reaction time of the screen. The 02 Prius reacts must faster.
It should not be showing power to wheels if you're stopped and braking firmly...it will show power to the electric motor and battery. If you are, indeed, seeing wheel turn when firmly stopped for a full 3 seconds I'd consider that a problem. There is a second or two delay b/w what's really happening and what's displayed on the MFD...that is normal.
Actually, I did some personal practical research. If you are not moving over 1 MPH, the wheels on MFD are not moving after a second or two. So if you are stopped for more than a few seconds, and wheels are still moving, something is wrong. You can see energy go from battery to wheels at a full stop with light brake pressure, but wheels still don't show moving.
