Gen 2 12v battery went from 12.8v down to 5.8v overnight. Just had it load tested yesterday.

Wonder if this could be a DTC C1377 - the brake control power supply capacitor bank could be bad. It's the black box near the 12v battery.

That O is a 0 (zero), and if you're getting a P0a80 then that HV battery is on borrowed time. Still the original OEM, and at how many miles?

 

See the link in post #16 for Gen 2 OBD2 scanner options.

How old is your 12v battery?

Posted via the PriusChat mobile app.

 

A little web searching suggests that dome lights are often either 6W or 12W, equivalent to .5A or 1A. Apparently the Prius is the former.

There are off the shelf LED replacements like this one:

(ack, link won't stick in post. Go to amazon and search for "Alla lighting de3022 de3175 LED Bulb 31mm")

which is a 1.2W device. That would be around 100 mA. Might not dim like a regular dome light, not that that feature is very important.

What is the point though? Unless a person leaves the doors open a lot the dome light isn't on very long.

Still, if we are going down this road, a circuit which would disable the dome light when there is adequate ambient light could save your butt while working on the car during the day with the hatch open.

Or maybe the dome light already turns itself off after a while even if a door is open? Not sure, never left one open that long to check.

 

Yes it does shut itself off. The map lights, if manually turned on, will stay on. The rear hatch light will stay on if the hatch is not closed well, a common issue and one where a led makes sense. The headlights will stay on if they are manually turned on with the car off.

An obd2 scanner will remain powered if left in the obd2 socket unless it has sleep mode based on lower voltage sensing. Typically aftermarket addons can be a source of parasitic draw as well. Particularly alarms and remote starters.

 

Hopefully you measuring amps and not volts now.

Realize you are working on one of the most complex cars ever made without the advantage of training, tools or experience. It is possible that one problem has become two due to mistaken assumptions.

Everytime you disconnect the 12v at the fuse box or at the negative battery, you will get high amp draw when you connect. Well over 25 modules are powering up each time.

If you have a new 12v battery now, forget about the parasitic draw until the car runs.

It does take a couple of Ready start attempts after reconnecting a 12v battery.

It is very possible the orange hv disconnect is not plugged in completely and or your fuse pulling has resulted in the wrong fuse in the wrong spot. Which can blow a small fuse placed in a high amp circuit, or leave a critical circuit without a fuse.

Finally, there is a very real chance your hv battery is bad especially if you still get the same code after installing a new 12v battery. Disconnecting the 12v temporarily clears the code, which you saw before, but the code will come back quickly after the engine starts for a short time. If the system realizes the hv battery is still bad it brings up the light show on the dash.

Orange HV Reconnect - Three Steps

 

The contactor in the hv battery is not directly energized by 12v. A cpu in the battery assembly is on a network with other cpus like the ecm and pcm who are running the show.

 

Tech stream is best. After that, it gets fuzzy because they are all a little different, and it depends on what ecu you’re trying to read, and if there are subcodes.
Torque, hybrid assistant, there’s a page in the technical forums with recommendations

 

All the way back in post #16 is a link to a thread that discusses Gen 2 OBD2 scantools.

Read the complete linked thread.

Posted via the PriusChat mobile app.

 

Tech stream and the connections are cheap. Then you need an old windows laptop and a lot of tech savvy

 

That sounds like a good plan. I would find the thread on readers first.
The crunchy brakes are just rusty rotors. You can wear it off by putting it in neutral at low speeds and applying the brakes gently.
Lights are meaningless without codes

 

Techstream officially is $75 to buy an activation that is good for two days. You keep the software, and you keep whatever dongle you buy to use with it, but when the two days are up it stops working, until the next time you pay for another two days.

Two days of use will cover most weekend car repair projects, and $75 is definitely cheaper than going to a dealer one time to have them use their copy of Techstream and tell you what they saw. And it's way cheaper if during those two days you use it multiple times to try things out and check them; try doing that in multiple trips to a dealer.

So in that sense it's kinda cheap.

'Unofficial' downloads of Techstream that have maybe 'forgotten' how to check your activation status are, of course, even cheaper than that, but not everyone wants to go there.

As for the dongle you use for connecting it to the car, any J2534 dongle is supposed to work and it's up to you which one to buy, so you've got lots of choices, but the one Toyota tests with and recommends is around $500. There are alternatives around the $200 ballpark, and the $100 ballpark, and the $20 ballpark, depending on how interested you are in putting up with their quirks. The recommended one might be the only one that's really quirk-free.