Prius: transmission lock error may mean tired 12 volt battery

[marsden_online]

I've had a generation 2 Prius for about 8 1/2 years and it's been mostly well behaved. Lately it started throwing up a few issues, particularly this one:



which I've seen occasionally before but has never really been a problem.

The following report is modified from my email reports to the local Toyota service center

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This time around however it was likely to appear already on a flat surface as on any sort of a slope and would not allow the car to be turned on when it present (which kind of removed the option to move to a flat surface if not already there). Applying the hand (parking) brake in and of itself appeared to have no effect and power cycling solutions (see below) didn't seem to be dependant on the handbrake being on or off - but I usually had to try several combinations before it worked so I could be wrong on that.

At various times this error appeared
- when I attempted to start the car
- when I went to turn the car off
- after I had taken the key out and was about to exit the car
- when I was away from the car (returned to the car to find this message)

Sometimes it appeared with a full array of dashboard lights, sometimes only one or two of them will be lit (which vary). On one occasion it refused to let me even power off the car and remove the key for about 5 minutes.

Since it started to be an issue I was able to get past this message by
- pressing the power button about 3 times about a second apart with my foot on the brake (initially)
- Repeatedly powering off and on the vehicle
- the last couple of times I had to get out and physically rock the vehicle to resolve the issue

[aside: When you have to push-start your Prius you're doing it wrong]

There were a few other quirks I notices in conjunction with this - sometimes the radio would be turned off when the car got started again and sometimes the temperature setting would have set itself to 25 degrees.

[I took the vehicle into the service center but they were unable to identify the issue at this stage.]

Eventually it got to the point where it started to develop symptoms which according to the manual translate to "take vehicle to your toyota dealer immediately" including

- no response to key/attempts to start meanwhile "engine" light on dashboard lit and light on 'park' button flashing . Fortunately rebooting (press power button 3 times) seemed to bring everything back online - sometimes after a significant delay and sometimes still had to get around parking error afterwards
- ! warning on dashboard and on screen appearing when car is started and not disappearing while driving
- ! light and parking error message not vanishing once car is in gear and moving (remained for duration of trip)
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Back in to the service center - had arranged a tow but tried one last time after emptying the car and it started so took it in immediately under its own power.

This time diagnostics indicated a low voltage issue with the little 12 volt battery which runs the electrics - lights, windows etc. Replaced that and the car has been running perfectly since. Well it had done 8 1/2 years - that's pretty good.

As an aside the service centre commented that my car is a "very well behaved" Prius but also noted that most people who take in misbehaving Priii haven't been bothering to get them serviced whereas I make sure to have mine checked annually. I just don't grok people who would front up the purchase price premium of something this full of complicated technology and then scrimp on the relatively trivial cost of the maintenance.

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