Slide backward on hill dry pavement, hot day

I think you mean that you are rolling, not sliding backward. If so, I suggest that you give this a try, if you have not yet done so: When you are ready to move on, press the brake pedal REALLY HARD and then quickly move your foot to the accelerator and hit the gas. Pressing the brake pedal in this manner activates the brief hill-holding mechanism, and by so doing may solve your sliding/rolling problem. I hope so. I have no clue about the other symptoms you describe.

 

Brian -- welcome to PriusChat!

It does sound to me as though the Hill Assist would help you. If you haven't tried this, just follow the basic instructions noted above. Once you press the brake very firmly, you'll get a flashing light on the dash and an audible signal that the Hill Assist is active. This will hold the car in place for up to two seconds, allowing you to move your foot from the brake to the accelerator.

If you've already tried this, and you aren't getting any progress, then you may have some more significant issues.

You've noted it is hot and you hear the battery fan come on. Are you using A/C? It is important to keep the battery cool.

By the way, you posted in the Prius v forum, which is for the 2012 Prius v Wagon, not the 2010-2011 Prius (Hatchback) Model V (or 5). I'm certain one of the Moderators will be able to move this thread to the appropriate forum -- nothing to worry about.

 

I'll take your word for that. It sounds like either a software or battery issue. Given the age of your car, it doesn't seem like it would be a battery problem.

Just for the record: Have you used the Hill Assist function in the past? Is it available right now?

 

You should have the dealer check it out as it sounds like a serious safety problem. Others have mentioned the hill-assist feature and it's important that you know how it works. I had a problem somewhat similar to yours because I didn't know how to use the hill-assist feature. The problem with hill-assist is that it only works for a couple of seconds. When I stopped on a hill for a red light, I pressed the brake pedal hard all the way to the floor thinking that that would engage the hill-assist. What I didn't know at the time was that the hill-assist braking expired after a couple of seconds and when I moved my foot from the brake to the gas, the car rolled backwards. Here's the proper way to use hill-assist: Press the brake only enough to keep the car from rolling backwards. When the light turns green, press the brake pedal all the way to the floor until you hear a beep. Then move your foot from the brake to the gas (without pausing for more than a couple of seconds) and the car's brakes will be locked until you press the gas pedal.

I think your problem may not be related to hill-assist because you mention that the traction battery doesn't seem to supply power to the wheels when you press the gas pedal and you have to wait for the gasoline engine to start up before you have power to the wheels. If that's the case, you need to see the dealer.

 

Brian, do you have a '12 Prius v wagon?

 

If the car believes you are pressing the brake pedal at all (either you are placing a small amount of pressure on it, riding it with your other foot, or the brake pedal sensor is not aligned totally correctly) then it will not listen to the accelerator pedal input (Brake Override function). If you did this on a steep incline and were touching the brake pedal so lightly that you weren't actually engaging the brakes but just triggering the sensor, this is exactly what would happen.