2005 prius will not start but 12v battery seems to be working

Does the door ajar light come on when you open the driver door?
I can understand how frustrating this must be. Even if the FOB circuit board is damaged, the RFID chip should be recognized when the fob is inserted into the key slot.

 

Don't, it is not the problem and won't fix anything – your doubts are justified. It will just cost you a couple hundred dollars of disappointment.

 

And for about the 4th time in this thread, those functions are TWO SEPARATE THINGS within the same physical device.
The money you are about to spend on a battery likely would be MUCH better spent on a visit to a Prius shop.

 

maybe a bad fob slot or power button

 

Check the door ajar indicator lamp by opening doors other than the driver door. See if it works for any other door. If not, my first thought is you have a loss of power on that circuit. If it works for other doors, it's probably a door position switch or wiring issue on the driver door.

Ok, so if you were to approach the car (with no FOB on your person) and look inside you should see the "flashing car with key inside" blinking every second or two. That's the immobilizer/theft deterrent indicator light. As soon as you open any door, the door ajar light should illuminate on the dash, the two green lights on the key slot should illuminate and the courtesy light at the bottom edge of the door should light up. If you sit in the driver seat and put your foot on the brake, the brake lights should illuminate. Press the power button and you should get a beep, plus the large "key with an exclamation point" (SKS warning light) should illuminate next to the immobilizer indicator light.

The above is what should happen when the car recognizes there is no FOB in range. Does this happen? If it doesn't, what is happening that's different?

Have you ever had your combination meter (the main "speedometer" display) suddenly turn off while you were driving?

And just to throw a WAG out there, the IG1 relay supplies power to the SKS ecu and Body ecu through the 7.5A ECU-IG fuse, and the combination meter through the 10A GAUGE fuse. You can pull those fuses and check to see if you have 12v at one side of those fuses. There should be 12v on one side, if not I'd say the IG1 relay is stuck open. Just a WAG, without being there.

 

Also, the KEY button on the dash under the steering wheel must be in the "out" position to have the SKS functional.

 

Geo,

I just went out to my car without a fob and did the exact same thing. Except I did it about 50 times because I pulled one fuse at a time. I went through the sequence with each fuse removed (from the underhood and under dash boxes) and the ONLY one that gave the exact same symptoms was the AM2 fuse. Every other fuse, when removed, still allowed the SKS light to illuminate and one warning beep if the power button was pressed. When the AM2 was removed, the door ajar and the car with key symbol were still flashing..but absolutely nothing happened when the power button was pushed.

Of course, the power button itself could always be the problem.

 

maybe

 

Check that the wire connector in the back is connected. Other than that, it might be a case of seeing if you can find a cheap one at a pick-and-pull place and doing a swap.

 

A diagram of the power switch, in case that helps you.
There's really only two options left.

1. The switch can't function because it's not getting power to it (or it has no ground connection for a complete current path) (or as mentioned above, the harness connection is not-so-good)
2. The switch is bad.

And...looking at the drawing, it appears the switch actually applies ground to pin 14 and 37 of the Power Source Control ECU when it's working properly. So either the switch isn't working or the PSC ecu can't tell that ground has been applied because it has something going on.

That pin 6/5G/5L/J25 Junction wire goes straight to the Left Cowl Side Panel body ground connection