Replaced 12V battery...still won't start normally, no brake lights, traction control light

New to Priuschat -- we have a 2010 model III with 94k miles, garaged each night. Recently didn't start on cold morning, so I attributed it to the 12V battery. It tested bad, so I replaced it and measure open circuit voltage 12.7V, under load 12.4V with headlights on. With the usual starting procedure the information display reads 'Depress brake pedal to start'. I removed the brake switch and verified that both pairs of switch contacts change resistance when the switch is depressed (one pair from closed to open, the other pair from open to closed). With the switch reinstalled, it only starts ('Ready' illuminated) while depressing 'Start' button for about 8 seconds while steadily depressing brake pedal enough to activate brake switch. The Traction Control light remains illuminated once started and the brake lights do not illuminate when braking (this is also true when the vehicle is off). Vehicle may be subject to Safety Recall D0H (D1H) for brake booster pump assembly (accumulator) but I didn't have it checked yet and don't think this is causing the issue. Any ideas?

 

I inspected the switch range of motion while depressing the brake pedal. I also hear a click sound which I interpret as the circuit closing (or opening). One thing I have not yet checked (due to safety of not having the brake lights working) is driving it at speed and setting the cruise control to see if it brake pedal deactivates it but I believe that is another switch anyway.

 

Do you have any recommendations on a OBD code reader? I read that switches rarely fail, but could try a new one as well.

To answer your previous post, the open circuit voltage on the old battery was 12.7V but I didn't read it under load. I simply noted slow wipers, slow power windows, and weak headlights before removing it and taking it to the shop to test it -- old one failed their test, new one passed same test.

 

I also found it strange that it would go to Ready after that long. At first I was going on the theory of an intermittent brake switch contact and pumped the brakes while pushing the start switch for an extended period of time. After testing the brake switch I tried depressing and holding the brake pedal and I got the same result after 8 seconds, and it consistently starts that way. Thank you for the recommendation on the MiniVci and we still do have a 32-bit laptop kicking around the house.

 

Fuse #14 (STOP), 10 amp, in the left side instrument panel fuse compartment under the dash turned out to be blown. Replacing it brought back brake lights and also normal starting action. Still have the traction control light on so I may go searching for another blown fuse or perhaps try the traction control disable procedure to see if that corrects it.

 

I disconnected the negative side for the time you recommended but the traction control light didn't go away. The time was sufficient to reset the clock and trip data, but not long enough to reset the radio presets. Also the GoPoint technologies OBD reader didn't see any codes.