My 2015 Prius plug in sat for too long and the 12V died. Ran a trickle charger overnight and no dice. Bought a replacement 12V and installed and lights turn on, horn beeps and display tells me to depress brake hold key to power switch. Again, no dice. I replace the fob battery and the light on the fob turns on when I hit a button, but it does not unlock car or allow me to start the car normally or by touching the start button with the key itself. I’m concerned, as it seems the implication is the car no longer recognizes this fob since it won’t even start with the powerless emergency method of touching the fob to the power button. I’ve seen threads on here reference an SKS deactivation switch or series of events to trigger SKS deactivation but can’t seem to locate a switch or get the magic steps to work. Any help is appreciated!
SKS being deactivated should not stop the ability to start the car with the transponder held against the power switch, and the fob battery is not required for this either. I would suggest trying to get this working before investigating SKS issues. Make sure you're following the instructions correctly for starting directly with the transponder. What is the 12V battery voltage when you're trying to start? Maybe it's still too low. There is no manual way of deactivating SKS in the Gen 3 Prius AFAIK.
I mean, I think I am. I've tried close to 100 times pressing the brake pedal and holding the key to the button in a variety of different angles, I just don't think it's recognizing the key. It's a brand new battery I bought from the auto store so I'd be pretty disappointed if that is the problem. Nonetheless if I can't find another solution I'll have to get a voltmeter to check. I'd assume that the alarm, lights, and dashboard all functioning is an indication that there is some voltage but for it to start it might be too low?
Local Toyota dealer is quoting me $140 to reprogram the key as they think I screwed something up when connecting the new battery. Gonna have to get it towed to the dealership.
Starting the high voltage system requires a lot more current than all that auxiliary stuff, so the battery could be at a low state of charge that's good enough for them but not starting the car.
Check the new battery's voltage, at the posts, and at the jump start location under the hood. It really makes no sense that changing the 12 volt battery would disable the fob.