dash ABS and all lights pertaining to brake system are lit.

It will be helpful for you to post the brake-related trouble codes from your car so that we can begin thinking about what the problem(s) might be.

If you don't have a scan tool able to read the trouble codes, you can also use a short length of wire and get the codes by counting light blinks, as you can find described in lots of posts here on PriusChat.

-Chap

 

have you tested the 12v yet?

how many miles on her?

 

Could some water have gotten in by the battery compartment? There is a capacitor for the brakes there. Perhaps the connector got wet.

 

C1241 refers to unexpected voltage being measured at certain points internal to the brake system. It's not impossible for this to be related to the aux battery, but not a sure thing either; wiring, connections, or relays bringing power to the brake system can definitely be at fault.

Internally, the brake actuator is split into two similar systems, "system 1" (powered by the ABS no. 1 relay), and "system 2" powered by the ABS no. 2 relay. Depending on what you used to read codes, you may be able to read a "detail code" for the C1241. If it's 81, then System 1 detected the issue; if it's 82, it was detected by System 2. Codes of 83 and 84 are also possible; they refer to the backup power capacitor module, or to a call for ABS "when the power source voltage of the main relay system is dropping", respectively.

System 1 and System 2 have essentially identical detecting conditions: insufficient current reaching the linear solenoid when the brake is applied, or a voltage reaching the BS1 (respectively, BS2) terminal below 8.9 V for 3 seconds or more while the brake isn't applied, or the internally-regulated 5 volt supply going outside of 4.7 to 5.3 volts for more than a twentieth of a second.

There are 8 pages of workup steps for this code in the repair manual, to pin down what's at fault. They do begin by checking to make sure there are no DTCs from the hybrid system (were you reading codes with a tool that can read the hybrid codes?), and checking that the aux battery is in the range 10 to 14 volts, charging or replacing it first if below.

C1256 has to do with inability to pump up a suitable pressure in the accumulator. It can also have detail codes, 141 or 143, whose meanings are distinguished on the first of the two pages of workup instructions.

C1344 reports a problem controlling the pressure in the left rear brake line. That can involve a leaky line, leaky SLA valve, leaky SLR valve, air in a line, or a warped rotor (not sure I've ever heard of that happening to a rear drum though). Detail codes (581 to 585) can distinguish some of those cases. Eight workup pages in the manual.

-Chap

 

Toyota makes it available at techinfo.toyota.com for (new pricing!) $20 for two days of access, $90 for a month. You can print-to-pdf portions of it you think you might refer to later.

Elektroingenieur has posted about options that may be available through your local public library.

 

Plus here is a tip on how to set up your computer to print those pages
Toyota TIS download tips | PriusChat
I would set it up and make sure it works before I paid the 20 dollars. Good time to download any other Toyota manuals you need at the same time.