12v Battery drain and DOME fuse

The car must be locked as well, to ensure the lowest possible quiescent current draw. If your car has the Smart Entry/Smart Start system then keep the fob at least 15 feet away from the car.

Electrical wiring diagram: techinfo.toyota.com which is a subscription website
Combination meter: it is located within the dashboard. Easy access: not really, you must remove the dashboard for access.

 

I've got an 07 that's doing almost the exact same thing. I'm waiting for tis to activate my account so I can pull a schematic. For some reason, I can't log in.
The draw is .3A until I open a door. It goes up some, and then drops back to .3A when the timer shuts the light off after closing the door. I'll post what I find as soon as possible.

 

Have you tried pulling the DOME fuse to see how that changes the quiescent current draw?

 

Yes, just like LBH's, it goes to 10 mA with the fuse pulled. That's the only fuse that caused a drop in amperage.

All the door switches are opening and closing and causing the amperage to increase/decrease as expected. I'll go check the front door courtesy lights. I don't remember if they came on or not.

 

The 15A DOME fuse feeds many circuits that require continual 12V power:

ABS, TRAC and VSC
Air Conditioning
Automatic Glare–Resistant EC Mirror
Automatic Light Control
Back–Up Light
Clock
Combination Meter
Cruise Control
Door Lock Control
Engine Control
EPS
Garage Door Opener
Headlight
Headlight Beam Level Control
Interior Light
Key Reminder
Light Auto Turn Off System
Luggage Compartment Door Opener
Multi–Display and Audio System (Built–in Amplifier)
Multi–Display and Audio System (Separate Amplifier)
Power Window
Push Button Start System and Hybrid Vehicle Immobiliser System
Rear Window Defogger and Mirror Heater
Seat Belt Warning
Shift Control System
Smart Key System and Wireless Door Lock Control (w/ Smart Key System)
SRS
Taillight and Illumination
Theft Deterrent
Tire Pressure Warning System
TOYOTA Hybrid System
Wireless Door Lock Control (w/o Smart Key System)

The electrical wiring diagram shows various junction connectors which distribute the power from the DOME fuse. So you would first have to understand the nomenclature for the connectors, then find where they are, then take apart one at a time to see where the 0.3A current draw is coming from. That would help you to narrow down the circuit causing the problem.

Overall this is going to be a very big PITA to figure out.

 

Door light

Ohhh yeahhhh!!!!!

 

Gonna be one of those back burner projects!

 

techinfo.toyota.com to get the electrical wiring diagram.
I do not know the locations, you will have to do some homework to figure that out.

 

Ok, got an update that hopefully will help here, LBH. I decided to drop the car off at the dealership since I have more projects than time, and I have a dealership/technician that I can count on. The tech found the drain in the combo meter late yesterday evening. This is for a car that I have a buyer coming for Monday, so I immediately called Matt at Texas Hybrid Batteries. He was able to send me one overnight today, so I'll have it in time to install before Monday. That was a big life saver!
The tech said that he has encountered a handful of parasitic drains in the Prius, and most of them have been the combo meter. Matt shared some insight on some that he's seen blowing a small internal fuse. Makes sense if the combo meter can potentially have a draw on it. I'm sending my core in for him to examine and hopefully find what's causing the draw.

In a nutshell, hook up you ammeter and then unplug the combo meter to see if the draw goes away. If so, call Matt at Texas Hybrid Batteries and he'll get you fixed up. If not, keep checking the rest of the stuff powered by the dome circuit. Good luck with it!

 

Thanks for actually replying, your answer will someday help others here. How does one unplug the combo meter? Can it be done without removing the upper panel?

 

You're very welcome Skibob.
I wish I could say yes, but I can't. Gotta raise the dash panel. Be careful with the a/c vents. They can be broken when trying to pull them out.

 

You're welcome. I hope this fixes yours. Take your time and be careful and you should be ok. If you still feel it's over your head, acquire some help. Contact Matt if you need a new meter. MUCH, MUCH LESS than buying from a dealership, the miles will be matched to your existing meter, and it will have a lifetime warranty!

 

Call Matt at (817) 629-8394. You'll want to swap it for a newer one so it will start registering miles again. You just have to change 2 boards instead of one. Piece of cake.