Hybrid System Malfunction, Pre-Collision System Malfunction

Out of nowhere, my 2017 Prius 4 Touring with 26k miles, owned since new, shows the 2 error messages in the title. I believe it also showed an ICS system malfunction when it first failed to go to Drive mode. (I'm not sure whether or not it was in Ready mode, at that point, but it would not go out of Neutral.) I immediately suspected a weak 12V, based on others' experiences with seeing a whole set of seemingly random errors. Sure enough, I pulled out my jump pack and after leaving it connected for several minutes, I was able to drive the car the 5 miles back home. Ironically, the failure occurred in a Harbor Freight parking lot, just after I bought one of those $75 AGM 12V they sell, that I intend to use for a shallow well pump. (I immediately started comparing the size of that battery I had just bought to the one in the car, but knowing HF's reputation for products of uneven quality decided it will remain to be used for a less critical application.)

So I was none too comfortable driving the car home with the 2 messages, as well as the amber triangle on the screen, but it was 7 PM on a Friday night and it was only 5 miles. Also, I didn't have the Android tablet with me, on which I have installed Carista, Dr. Prius, Torque Pro and Hybrid Assistant. (Silly me, I didn't think I would need those tools for our 2017 Prius, I use them all with the Gen 2, along with Mini-VCI cable for Techstream that resides in the console of the Gen 2. The Gen 2 is currently being used by my wife in NY and giving her no problems, I am presently in Florida).

So I got home, put the charger on the 12V overnight, and this morning installed Carista, Dr. Prius and Torque Pro on my phone. Torque Pro and Dr. Prius do not report any error codes. Carista reports C1A63 from the Pre-collision system 2 ECU, and P058A01 and P06881F from the Electric propulsion control ECU. I do not get any hits on those last 2 codes when searching either Google or PriusChat. I was able to clear the first code using Carista, but not the last 2. Still thinking the 12V might need replacement, I drove a few short blocks to Advance Auto Parts to have it tested. They tell me the CCA they measured exceeds what is shown on the battery's label, so it is fine.

Now I have an appointment at the nearest Toyota dealer's service department Monday morning, but I'm wondering what this will cost me. (The 20K mile check, consisting of an oil change and tire rotation at that dealership was $239). I'm also considering a 2 day subscription to the TIS web, but without having my Techstream equipment with me, it would seem like it might be a waste of money. I will probably end up disconnecting the 12V to see if that does anything, but I really do not want to lose my radio and navigation settings.

Story to be continued.

 

I still suspect the 12V battery is at fault. Part of the problem is I'm not sure what is normal behavior for this car as compared with the Gen 2, which I am much more familiar with, having put 80k miles on it over the last 5 years.

When I got out of the car to go into Harbor Freight yesterday, I'm sure I turned the car off by pressing the Power button. With the key in my pocket, I opened the door to leave and I heard the car making a "dinging" sound. I didn't think I usually heard that under those conditions, but I wasn't sure. When I came back to the car, I'm sure I put my foot on the brake and pressed the Power button, but I saw the whole array of lights with the amber triangle, at which time I also saw the 3 error messages on the screen, repeating one after the other, for the hybrid system, the pre-collision system and the ICS (Intelligent Clearance Sonar) system. I then found that I was unable to move the drive control stick into anything other than Neutral. I just went out to the car again now, and I discovered that that behavior is exactly what you would expect if the car is in IG-On mode, rather than Ready mode, except that those error messages would not normally appear. When I went out just now, I took my multi-meter with me and measured the voltage on the battery at 13.53V, mainly because the solar panel charger is still attached. And wouldn't you know it, now when I power the car on, there are no more messages. I went out prepared to disconnect the 12V, but it appears that will not be necessary.

To answer your questions, @bisco:

Yes, I'm sure I tried to power the car on several times yesterday and it would not go to Ready mode, but it did on the first attempt after the jump pack had been attached for several minutes.

I leave the solar charger on it all the time, unless I'm driving it, and whenever I've measured the voltage during the daytime with the solar panel attached, it always reads above 13V, which tells me it is working. When I measure the voltage in the morning before direct sunlight hits the solar panel, it is usually around 12.5V. When I got home yesterday, after nearly getting stranded, I immediately plugged in my 4 Amp charger-maintainer and left it on the battery overnight. This morning, according to reading on the charger-maintainer, the battery was fully charged, because it did not show the graphic that it normally does when it is still charging, and the voltage read 12.7V. When I opened the door, with the charger still attached, the voltage reading dropped to 12.4V, so I waited for a few minutes until it had charged up to 12.7V again before unhooking the charger and driving to Advance Auto Parts.

I wasn't so concerned with the voltage reading (I knew what that was) as I was with whatever other function they perform to determine the capacity of the battery. I couldn't see what they were reading on their device, but they did look at the label on the battery which says it should have Cold Cranking Amps of 295 and then they said their reading was more than 300, so they believed the battery did not need to be replaced. They had a DieHard in stock that supposedly fits the car, which I was prepared to buy, so I did not question their judgement that the battery was fine.

As I said, I leave the solar charger on the battery at all times, which I thought was the right thing to do (we also leave a charger-maintainer on our Gen 2 battery, which is now more than 5 years old, and that seems to keep it in good working condition). So I'm going to cancel my appointment with the dealer's service department on Monday and finish running the errands with the car that I was unable to complete yesterday. I'm not going anywhere without that jump pack that was also freshly charged overnight, though.

 

That wouldn't explain the error messages, though. Funny how one incident like this damages your confidence in the car. For the next little while, I'm going to be extra paranoid. At least I got through the rest of my errands this afternoon with no further issues.

As always, thanks for your feedback.

 

I was unaware of that because I almost never touch the power window buttons, after having to replace the power window motor on another car we had. When entering or leaving a parkade that requires getting a ticket from a machine or putting it back into the machine, I will even open the driver door rather than open the window to get it or place it, unless there is a long line of cars behind me. None of the windows had been opened this time either, I'm still at a loss to explain what was going on. A depleted 12V is still my best guess, but I had been driving the car almost every day for 20 miles or more, and had driven about the same distance that day, making several stops before this happened, in addition to always keeping the battery on the solar charger when not driving it. I like the theory that the brake switch may have been acting up to explain why the error messages appeared and the car would not go out of Neutral, but that wouldn't explain the dinging I was hearing upon exiting the car before anything else happened. Also, I was able to lock the car upon leaving it, even after hearing the dinging.

 

That one incident is the only time I've ever had a problem with the car in (now) 5 years of ownership. I never took the car to the dealer to have the issue diagnosed, and it has not recurred. The weather was fine when my issue arose, and as far as I can remember, had been fine for several days earlier, so I suspect the cause in my case is different than yours. I wish you the best of luck. If the messages have gone away, I would not bother taking it to the dealer. If the messages cannot be reproduced by a particular action or condition, they will not pursue the cause, which is probably to your benefit given their shop's labor rate.