Car stops when I go downhill and need to stop the car

The car will go into Park if you stop and then press the Park button. Or it will automatically put itself into Park if you turn off the car with the Start button.


Ignore my comment below that I grayed out since I couldn't find a line out. @ChapmanF corrected my misunderstanding below in #38. Thanks, Chap!

The 12V battery closes a relay that connects the big battery to the car and it also powers the computers. There is a mechanism in the transaxle that engages a "parking pawl" with notches in a part of the transaxle shaft. It is held out of Park electrically so, if the voltage on the battery gets too low to run the computers or keep that relay closed, that will release the parking pawl and the spring will engage it. If the car is moving when that happens, it could cause serious damage.

 

you might also have a bad display. are you not getting any warning lights on the dash?

 

the p button only puts it in park. pressing again doesn't do anything. you need to put your foot on the brake and use the shifter.

 

are you going to try to fix it yourself?

 

no. it should not place itself in park every time you stop. it works like a regular car, except the engine turning on and off as it is programmed.

 

got it. that is very strange. is there someone that can test the 12 volt battery for you? or charge it?

 

the hybrid battery is a few thousand dollars here. the 12 volt battery is around $200. can you buy on line?
if the hybrid battery is bad, you will get a red triangle on the dash. there is no warning for a bad 12v.

 

There you go. It's pretty nearly standard procedure to check the 12V battery when strange things happen. Once you know that's OK, then you can begin troubleshooting if there is still a problem. A low 12V can cause a variety of symptoms, but this is the first time I've heard of anything like what you are experiencing.

 

Just for accuracy's sake, it works a little differently. There's a (powerfully geared) small electric motor on the transaxle case, which drives the parking pawl into the parked or free positions. It has to be electrically driven in either direction. When not being driven, it just stays put.

It also has the odd feature that you can't just put 12 volts on it to make it spin. It has separate connections to several different pole coils, and the "transmission control ECU" has to make it spin, in either direction, by sending pulses to the right coils with the right sequence and timing. That makes it pretty hard to "hotwire", which is part of the design; because the car doesn't have a steering-column lock to serve as an antitheft feature, the difficult-to-spoof (and difficult-to-get-to) parking motor is what checks that box.

Needless to say, that makes it something that won't just happen to drop into Park because of a power interruption or something; the transmission control ECU has to really want to park you, and have power available to do it.

-Chap

 

All this talk about the 12v Battery being bad, but I have a question. When the car is in Ready mode, doesn't the DC-DC inverter supply nearly 14volts to the 12volt bus to charge the 12v battery? Once the car is in Ready mode, you should be able to completely disconnect the 12v battery and operate the car in every normal manner until you turn it off with the Power button. I just don't see how a bad 12v battery could affect the car when it is in Ready mode - unless it has an internal short dragging the voltage supplied by the DC-DC inverter down to less than something like 11 volts and I would think a fuse would be blowing at that point.

 

If the battery is bad enough, it will drag down the whole bus. Many amps can be drawn before it is a problem for a fuse. Additionally when READYing the car, it does some calibration and when the 12v is low, all these settings are wrong. It is quite possible this is 12v related. Especially since it sounds like it was shipped from Denmark to the Czech Republic to a new owner which means it sat for a bit.

The only way for the "P" to light up on the combination meter is if the car sends the CAN message to engage Park. There are no other ways of that happening, the combo meter only reads CAN codes.