No power off, bad graph, weird problems!

I'm hoping someone here can help me pinpoint the cause of some strange electrical problems my 2006 Prius has recently developed.

It started off this past weekend when I went to shut off the vehicle after about a 5 mile drive. The car wouldn't power down, though, regardless of how many times I pressed the Power button. I then noticed that the wheels on the MFD were still turning, despite the car being stopped and in park. I shifted to drive, drove a few feet, shifted to reverse, drove a few feet, then back to park. Same problem. (Note that I was able to shift gears without any problems despite the wheels on the MFD continuing to turn.) I finally ended up leaving the car powered on for about 20 minutes, and when I returned the wheels on the MFD had stopped turning and I was able to successfully shut the car down.

I drove it several times with no problems, but then experienced the same problem again yesterday. Also, I noticed that the bar graph of mpg seems to be showing about half of what the car is actually getting. I was on a long trip, and the car seemed to be getting about its usual 50mpg, but the bar graph consistently showed ~25mpg. The "instant" bar on the far right of the graph was correct, as was the overall average displayed on the other page, but the graph itself was clearly wrong.

Finally, and this may be completely unrelated (or not!), the CEL came on during my long trip. I took it to Autozone and the code set was P0011, which apparently indicates a fault with the VVT. I don't know if this is a separate issue, or if there's some electrical problem causing all of these symptoms.

In searching for power-down problems, it seems the two most common causes are a bad combination meter or a dying 12V battery. I haven't experienced any loss of the instrument panel display nor any problems shifting between gears, so I don't think it's the combination meter. My 12V is only a few months old and the connections seem to be good.

Anyone have any ideas that might save me an expensive trip to the dealer?

Thanks!

 

Well, as much as I would have liked this to have simply been a bad battery, that doesn't appear to be the case. I did the self test procedure, and battery voltage was 12.4 V.

Ironically, after completing the self-test, the car again would not shut off. Having read this morning about the 3-second power button push to power down the car, I tried that. It did indeed shut off the car, but the MFD stayed on. Is that normal? Now, however, the wheels on the MFD were not turning.

The problem then became how to turn off the MFD. By pushing the power button without my foot on the brake, it will go into accessory mode, but the wheels on the MFD start turning and I can't shut down normally. I discovered, though, that there's about a second between pressing the power button and when the wheels start turning. So by quickly pressing the power button twice from the powered down but MFD on state, I can get everything to turn off.

Any more suggestions out there???

 

Thanks for the responses. As for letting the battery sit overnight, you are correct cwerdna that I did not do this. However, even with the headlights on in accessory mode (hefty load), the voltage was still 12.0V. And again, the battery's only a few months old. So unfortunately I don't think a bad battery is causing this. I'll try to do the self-test again tomorrow morning just to be sure (didn't have a chance this morning).

Patrick, I'll give your suggestion a try, too. I looked over the battery connections and they seemed fine (tight, no evidence of corrosion), but I did not try disconnecting the battery for a few minutes. I'll give that a go this evening. Oh, and mileage is at about 112k.

If anyone has any further suggestions, I'd be happy to hear them!

Thanks everyone!

 

I forgot to include in my original post another symptom I experienced: the cruise control does not work properly. When going down the highway, if I set the cruise control to 65, it will hold 65 for a random amount of time (a few seconds to several minutes), but then it will start surging and hesitating. Eventually (sometimes quite quickly), it acts like the cruise setting has been erased. That is, it starts decelerating and hitting resume on the cruise control has no effect, but it can be "set" again, at which point the cycle repeats.

Just a little more info so hopefully someone can say "Aha! All of these symptoms indicate that your xxxx is faulty."

 

Well, here's the latest. I checked battery voltage this morning after the car had not been driven for many hours and it was at 12.5V with minimal load and about 11.9-12.0V in IG-ON with the headlights on. So it seems the battery is in good shape.

I did make a couple of observations when I had it in self check mode to test the battery, though:

1) When in accessory mode, the speed displayed was 0. However, when I went to IG-ON mode, the self check screen displayed 22 km/hr. The speedometer on the dash never displayed anything other than 0.

2) The "PKB" entry on the self check screen...I assume this is supposed to indicate whether or not the parking brake is set? If so, it did not work properly - it always said "Off" whether or not the parking brake was set.

3) The "REV" entry on the self check screen did work properly in that it said "On" when the car was in reverse and "Off" otherwise. In addition, the backup lights also work properly.

 

Unfortunately, disconnecting the battery for several minutes and then reconnecting it did not solve the problem(s).

 

Hmmm. Every description I've read of the bad combination meter problem has said that the combination meter went completely dark, and it was during this time that the driver was unable to power off the car. Then, at some later point, the lights on the combination meter would come back and power off would work. My combination meter has never gone dark, and the power off problem occurs (needless to say) when it is lit. Also, people seem to have indicated that the backup lights don't work when the bad combination meter problem occurs. My backup lights are working properly (see my post #10).

I suppose it's possible that my combination meter has failed in a different way than everyone else's. Do you still think it's the combination meter, despite the above?

At any rate, thanks for the suggestion!

 

Well, the speedometer display of the combination meter shows the correct speed. So it seems that the speed signal is getting messed-up somewhere downstream of that, either within the circuitry of the combination meter itself, or a wire/connection after the combination meter but before things like the cruise control, power button, and MFD. I've been trying to decipher the wiring diagrams of the repair manual to see if I can figure out some specific wires to check, but I'm having a hard time figuring out what goes where.

I appreciate the offer to meet up with your AutoEnginuity! I'm out of town the next couple of weekends, though. Hopefully I can figure it out, but I might ask to take you up on the offer at a later date. Now that I've figured out the 3-second power off trick (thanks Priuschat!), the car is at least drivable.