Brakes jerky and unreliable - Help!

Hello, I am hoping to hear any theories about what might be wrong with my 2004 Prius (123,000 miles).

For the second time in a month, while driving, the brakes have suddenly gone funny (for lack of a better word). When I first apply the brakes to slow the car, it initially does not respond, then, as I continue to gradually depress the brake pedal, the car will begin to jerk as if I am slamming on the brakes repeatedly.

Just before this symptom begins, the brake system warning lights and master warning light come on.

The first time this happened, I took it to a shop (not Toyota-specific) and they found that my floor mat had slid forward and folded and was under the brake pedal touching the wires. When they removed the floor mat, the problem went away. I threw out the floor mat and have been driving without one.

Today, the same thing happened again, with nothing obstructing the brake pedal.

I live in an area where the closest Toyota service station is an hour away, and I hesitate to drive the car that distance without good brakes. But I'm also reluctant to take it back to a service station that does not specialize in Priuses.

Any ideas or advice?

Thanks!

 

Thanks for your help. I am in the Bedford, PA / Cumberland, MD area.

Not sure if this is relevant, but I did have the heat on max heat when it happened -- I do this sometimes to help dry my hair on my way in to work (despite it being summer). May have been the same situation the first time, but I'm not sure. The problem did not go away when I started the car after having it off for four hours.

 

Also, when I took it into the shop the last time, they did read the codes and do some tests. Here are my notes from that report:
They said something about high and low voltage and asked if my battery had been jump started or weak lately (it hadn't). They load tested my battery and said it passed. And they found a code for a stop lamp switch, located behind the brake pedal, assocated with the electrical portion -- which I interpreted as being the reason why my brake warning lights frequently go on for no reason when the car is running fine. I was told it would be $250 to fix that issue, and I decieded not to, based on my guess that this only relates to the warnign lights going on without cause.

 

Thanks everyone for your advice. I ended up driving it an hour to a Toyota service station and they found that there was a bent pin on the switch that activates the regenerative braking when the brake pedal is pushed -- so it was relying only on the emergency brakes to stop. They replaced that for $280 (mostly labor) and all seems to be working fine now. That may have been what the first shop was trying to tell me and I may have misunderstood.

 

Yes, that seems like the most likely explanation to me, as well. I was aware of the floor mat recall but had decided to keep mine in anyway (until this happened)!