A PSA for Gen 2 Prius Owners...

Wow!

Nearly a month wasted and codes have not been read.

There is a known fault with the dash board lights going out. This is a separate issue than the ABS problems. You can chose to live with the dash going dark or have it replaced.

Stop messing around with paper clips and 12 volt batteries and get the codes read.

 

12.6 is a fine resting voltage. turn the headlights on and watch it for 5 minutes

 

sorry about the headache

 

Like the others have said, the engine being on or off can not make any difference here. You must mean when you have the ignition on ( car says READY ) or not.

 

Statements such as this one are where the confusion arises. IG-ON and READY are two different things.

	To get to this state ...	Do this ...	then this ...	Notes
1	ACC	Foot off the brake	press start button once.
2	IG-ON	Foot off the brake	press start button twice.	(Once again if in ACC)
3	OFF	Foot off the brake	press start button a third time.	(Once again if in IG-ON or READY).
4
5	READY	Foot on the brake	press start button once.

NB: Pressing the Start button once, with your foot ON the brake, from any of the above states (ACC, IG-ON, OFF), will start the car and make it READY to drive.

 

Oh yea... I guess there is that weird state between accessory and ready. What the heck is the deal with that? Is the HV on? If so then what is not READY about it? They just lock out the shifter?

 

That same deal as with regular cars when you turn the key to ignition on but have not started the engine.

Some of it. The inverter, for example.

 

ok, you keep saying the dash lights go out, WHY HAS NO ONE told you that the combination meters need to be replaced when this happens. No guages means the board is bad. SImple fix. Takes about 2 hours if you have never done it before. Good luck finding a used one that isnt also broken. Toyota wont sell a new one unless they keep the car for a week while they order one from Japan with the same miles programed on it. You have two seperate problems. ABS lights on could be a lot of things. Fix the combination meter first.

 

No need for luck. This guy is one of our most respected members.
Prius Speedometer Replacement

 

"self diagnostic"? If that's the car's "self diagnostic", the the car is very much on.

 

All is dark, cold, and lifeless in inverterland, in every mode except READY.

What ON gives you is all of the car's 12-volt equipment (dash instruments, heat blower, wipers, ECUs, etc.), but all being supplied by The Little Battery That Could Only Not For Very Long Under Those Circumstances.

The inverter cooling pump does run then too, even though there's nothing for it to really cool, just because ON powers all the 12 volt equipment and it's in that category.

 

Yes, totally agree... If it's one thing I learned during the pandemic is that a legit 12v battery charger is way more reliable than a trickle charger.

 

Funny, I think I must have stopped following the thread after that haiku, but it looks like the OP really did read for codes in the very next thread, it just wasn't very prominent and kind of got lost in other stuff.

So, assuming the first letter the OP wouldn't give was a C, then C1247 is a code for the pedal stroke sensor. It's got nine different INF codes to pin down what kind of problem, and five pages of troubleshooting steps in the manual for getting it sorted ... though this might be a little late for the OP's purposes.

"Messing around with paper clips" isn't always a terrible idea. You can use it to read the codes, which is what it's really for, and the OP could have had the blink code 47 in one try and never even needed the dealer to scan it. (The scanner is still useful for the INF codes, though, which the blinks won't give you.)

The only silly part about the OP's "messing around with paper clips" is that the OP was only clearing the code, not even counting the blinks to find out what it was.

And because that would cancel the fail-safe behavior for however long it took for the brake ECU to notice the stroke sensor problem again, the OP ended up jumping to this conclusion:

But the stroke sensor and its wiring are physical, and when something is wrong with them, the car isn't really operating "exactly as it should". There really is something physically wrong. Maybe you can't tell there is without the computer alerting you to it, but that's what warnings are for. A warning that only came on when you could plainly tell your brakes were failing would be more like a weather rope.