My Prius won't turn off — no, I mean it *REALLY* won't turn off

Have you tried holding the power button for a long time?

Have you tried pulling the electronic key out of the dash?

 

Unless DIY, you will find a quality rebuilt from Matt ( @Texas Hybrid Batteries ) : Prius Speedometer Replacement

Disconnect the 12v in the back right corner of the trunk, easiest way would be to disconnect the large white plug closest to the front of the vehicle (12v positive terminal) be sure to place a towel or rag between the hatch and latch so as to prevent the rear deck from closing. If you can't leave the vehicle unlocked, then lay the back seat flat and so that you can crawl into the rear area to reconnect the 12v later.

Reconnect the 12v when you need to start the vehicle, and it will take two (2) attempts before it actually starts upon reconnecting.

 

Is disconnecting connector F15 (seen in your photo) always enough? In the Emergency Response Guide (PDF), on page 16, Toyota suggests also removing the HEV fuse under the hood, presumably because the 12-volt bus might still be energized by the DC-DC converter if the hybrid system is running.

 

Guess we might find out, or she might run out of gas first.

Question, can you stop the engine from running by disconnecting the "dome fuse" ?

 

Just to avoid confusion, if the problem discussed in this thread is the typical one, described on Luscious Garage’s page and in many previous PriusChat threads, it shouldn’t be necessary to disconnect anything or remove fuses: as @JohnPrius3005 kindly mentioned, a long press on the power button is ordinarily enough to get the power source control ECU to turn off the power.

Removing the DOME fuse would prevent the hybrid system from being started, since it controls the +B1 power supply to the smart key ECU, but I’m not sure what the effect would be if the hybrid system were already running.

 

Hi Gwyneth, congratulations on doing what you did. You’re also quite courageous for going on the little trip you did and for turning your car off and on multiple times, knowing it was not certain to stop or start again.

I am certainly no expert. But I do have 3 Priuses that have similar, and other problems. I keep them limping along and have done so for a few years.

For what it’s worth here is some of what I do and my thoughts.

Turning the lights off and on and holding the info button is no secret solution. It likely changes some level of electric volts or amps just enough to get a failed/failing component to work. But if it works then it works.

Your power button may be suspect but changing that is just throwing parts at the problem. So far I haven’t done that, but apparently it’s a lot easier than changing the combo meter.

Ditto with the 12 v bat. You will certainly get advice to change the 12 v bat. This has not worked for me. It may for you.

In my case my 12v bat discharges easily. I deal with this by disconnecting the big white plug to the battery every single time I power my car off! This has involved filing down the clips/latches of this white plug because it’s pretty hard to remove. Also making sure the mechanical key unlocks a front door.
And the back seat backs are folded down to allow access to plug the white plug back in. At home I prevent the “trunk” hatch back door from latching and always put a charger on the battery.

in addition my HV “big” batteries are also problematic so I’ve built cheap grid chargers and wired them in and charge the HV batteries overnight from time to time.

All of this is still I think easier than changing the combo meter! Although I may be wrong about this. And I doubt the combo meter is the cure.

It is possible to fix these problems and others with Priuses, but it’s not easy. Many here are far better at it than I am.

Another thing I do is have multiple vehicles although that too has failed me.

You will and have learned a lot dealing with your old car.

Good luck. A lot of smart highly experienced people on here know as much or more than the most highly trained Toyota Prius techs. And if you’re really lucky you may have access where you live to a good independent tech. But be skeptical. Confidence is no real substitute for real knowledge and skill!

 

As suggested upthread, the real, best, only solution is to fix that combination meter before the shenanigans get too much more inconvenient than they already are.

As Elektroingenieur pointed out upthread also, knowing how to disconnect the 12 volt battery in back is useful information for a lot of purposes, such as if you want to keep the car from starting, but might be of little use when the car is already in READY mode and producing its own 12 volts. My Gen 1 would never miss a beat if I disconnected the 12 volt battery while it was running; that was my typical procedure when offering jumps to other cars.

I think you'd probably get the car pretty much off eventually if you popped the hood and started pulling on fuses with names like HEV, AM2, and EFI, or under the dash with names like ECU-IG and IGN. Once the READY light dropped out (if you can even tell that on a flaky combo meter), it would no longer be making its own power, and you could disconnect the 12 volt battery in back and it would be well and truly off.

I wouldn't be too surprised if you reconnect the battery and fuses and it tries to turn on again. I think I've noticed that after a sudden power loss, it tries to return to the state it last remembers instead of just waking up and being off.

 

Hi Chap, As I think you know, you are one of the very smartest and most helpful people on here and I've learned a great deal from you, and others could do a lot worse than to paying close attention to your posts. Thank you for your generosity.

Do I understand correctly that a failed or failing combination meter can cause a lot of hybrid problems, and is not simply a "nuisance" of having no display? If that is so, I'd better get good at replacing or repairing my combo meters.

Aloha

 

One of the biggest nuisances associated with the combo meter failure, in a lot of threads here, is the eventual inability to turn the car off, which can become a pretty big nuisance.

 

Thanks!

 

Do not forget that when the car does not turn off while the combination meter is defective many times the trunk does not open as well. Then you need to crawl in the trunk from inside and open it to access the battery white connector.

 

We have a very well travelled '08 Prius that often looses it's combo meter and the hard to turn off problem. So far it eventually turns off, but we found combining a turn signal switched on often helps with the no turning off and being able to get the combo meter back on with the info light flash fix .... or undoing the cable under the red cover under the fuse box near the left hand headlight. The rear hatch does open once you get the car turned off when the combo meter fails.
We found an app on the smart phone to give us a speedo when the meter decides to play silly buggers so that gets us through that problem.
We also discovered the odometer doesn't record when the combo meter fails to light up and that really messes with the ltr/100km measurement and the expected 700km from each tank of fuel .... and the low fuel warning doesn't go off either, so a few panics as to just how much fuel we actually have left in the tank can occur .... so we've ended up also carrying a 4 ltr petrol can if we are travelling the 200km round trip to Adelaide and back to Mannum.
We paid very little for the Prius in the first place, it has cost us a catalytic inverter, tyres, oil and fuel over the last 40 something thousand kms, we want to see if it will keep going till we roll up the 1,000,000km on the odometer, so we don't want to replace the combo meter because we will loose that 740,000+ km reading we have now.
It is a reliable workhorse and we love it, so we just put up with it's few strange habits :lol:

T1 Terry

 

Another option is to replace the fractional-dollar capacitor in the combination meter.

This kind of intermittent issue makes a great psychology experiment; all the threads that talk about it demonstrate the incredible variety of interesting dances people come up with and can convince themselves are helping, as long as sometimes the car works when they do them.

 

A photo and arrow where the faulty device is located would be helpful a part number for the replacement part would also help lots :lol: I figured it might have been a resistor no longer draining a diode rather than the diode itself .... but I really didn't want to remove the combo meter and have a play with it in the hope I stumbled on the faulty part ..... I have enough to do repairing failed 24/240vac inverter/chargers/MPPT controllers to satisfy my curiosity for circuit board tracing plus trying to repower this early model electric car I bought a while back, a Blade Electron V

the one in the video is the same model as I bought and was originally owned by Ross Blade himself and in immaculate condition.

T1 Terry

 

Ummm, if you go to the top of this (Care and Maintenance) forum, you'll find the "sticky" posts. Fourth one down is "combination meter repair- DIY". Read that- it has the procedures and pictures in it, and somewhere has the part numbers from DigiKey for new capacitors.

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