Low 12-Volt Battery Apply Parking Brake Securely...

In Toyota’s Repair Manual, for the message you quoted, the Problem Symptoms Table for the electronic shift lever system lists only “Auxiliary battery is discharged or voltage is low” as a suspected area. The table refers to an “Auxiliary Battery Low Voltage” troubleshooting procedure, which in turn refers to a more detailed on-vehicle inspection procedure for the charging system and auxiliary (12-volt) battery.

With the car turned off and not charging, have you measured the voltage across the auxiliary battery? Could one of the aftermarket accessories have malfunctioned and be drawing current continuously?

Without a good 12-volt power supply, the hybrid vehicle ECU might not be able to operate the parking lock mechanism, so you could try to shift to park (P), but the lock pawl may not actually be engaged. In this situation, if you want to be sure the car won’t roll away, you need to use the mechanical parking brake.

As the New Car Features book says, when the message is displayed:

• The parking lock mechanism may not operate.
• The hybrid system may not be able to be started.
• Even if turning the power switch off, the power switch may change to on (ACC). In this situation, applying the parking brake may enable the power switch to be turned off.
• Even after charging the auxiliary battery, the message may be displayed until the shift state is changed from park (P) to a shift state other than park (P).

If the hybrid system, DC-DC converter, and auxiliary battery all OK, and there isn’t an extraordinarily high load on the 12-volt electrical system, then the auxiliary battery should be charged when the car is in “READY.” Considering the symptom you’ve reported, however, I’m not sure I’d count on this without further investigation, at least to check that charging voltage (13 to 15 volts) is present at the battery terminals.

Both the Repair Manual and New Car Features are available by subscription to techinfo.toyota.com.

 

What I notice in this picture is you are not in READY mode, but ignition is ON, so all power is coming from the 12V "aux" battery. I like to use a plug-in voltmeter to monitor the 12V level. Before you get to READY mode, you are seeing the voltage level of the "aux" battery alone. After READY mode is engaged, you are seeing the level of the 12V charging voltage that comes from the traction battery.

 

It's pretty straighforward: pop and raise the hood, set the multimeter to Direct Current Volt mode, red lead to positive (red capped) battery terminal, black lead to grounded bare metal, something like a bolt into the frame, or the engine. If your multimeter is not auto-ranging, you'll need to also set it to an appropriate scale.

The reading you get will something along these lines:



From this page:

The 12volt Side of Life (Part 1)

The multimeter will give you the at-rest voltage, a good first step, still it falls short regarding battery "health". Something like the Solar BA5 (or various similar iterations) are better in this regard

 

the car charger should charge the 12v while charging the hybrid battery. if you charged at the beginning of the 19 1/2 hours, and the 12v is actually discharged, something must be discharging it. either a light on, or a short.

does the car not start?

 

Two checks would clear things up a lot.

1. At the least a check of at-rest voltage. Or better, an electronic load-test with Solar BA5 or one of it's kin.

2. Connect the multimeter up in ampere mode, in series between the battery negative post and ground. Basically: disconnect the negative cable at ground, then clip one lead to that cable, and the other to a good ground on the car. Then just let it sit and see what kind of milliamperes you're reading. To protect the meter, start with the meter in ampere scale, there should be no reading, then switch to milliamperes.

Doing this with ours, I got around 16~18 milliamperes, with spikes to around 40. This is basically the background load on the battery. If it's signif higher, something is running your battery down excessively.

 

that would confirm the dead battery if it jump started. to know if it is charging the 12v with the hybrid, if you get a voltmeter, the 12v will read high while the car is charging.

you're not the first person with a dead prime 12v, so it might just be defective and under warranty.

 

i can't. i thought it was the same as pip. perhaps they changed it because the battery is in the engine bay.

 

no doubt @Elektroingenieur knows.

 

Yeah it seems like the BA5 is in short supply, maybe phasing out? If you're looking in Amazon, I've noticed a lot of alternatives, apparently better displays, and you can connect to your computer with USB, print out.

OTOH, the BA5 (or BA7) are tried-and-true. I've had my BA5 for 2~3 years now, and it's still fine, only the leads are slightly twisting, lol. It's rudimentary, but works. I'll sometimes take a shot of the display with my phone, if I want to keep a record.

To directly answer your question, I think I'd go for the BA7. I suspect the extras are more useful on a conventional car, with regular charging system, but you may encounter some of those. For $7 difference snap it up.

 

There is indeed such a converter. In New Car Features, Toyota writes, “Using the sub DC-DC converter built into the electric vehicle charger assembly, the auxiliary battery is charged with the minimum necessary power to reduce power consumption.” The Repair Manual has a few more details; see the procedure for diagnostic trouble code P1CCD96 and the explanations for Vehicle Control History codes X0543 and X0544.

That said, I don’t know about the output capacity of the sub DC-DC converter. It may be enough to keep the car from draining the auxiliary battery while it’s charging, but it might not be able to support much more in the way of parasitic load, much less recharge an auxiliary battery that has already been discharged.

 

I suspect when the car is off there's no charging of the 12 volt by the DC-DC converter; allowing that could deplete the hybrid battery.

 

correct, that's why i posted the theory in #7, that after the charging was done, something drained the battery. but maybe not.