One problem related to alternator/generator/regulator has been reported for the 2004 Toyota Prius. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2004 Toyota Prius based on all problems reported for the 2004 Prius.
Omg, omg its so fresh in my mind!. I was terrified. My daughter(oldest) was in a terrible car accident and was taken to the hospital(mary washington in va. ) I was at work and got the horrific call about 1745hrs (rush hour). I jumped in my car(2004-prius) I I can't tell you how I felt. As I entered the hov lanes from DC to va, my car started pausing. . I've felt this before, so I hit the info button and see my battery took over and is on 4 lines! I then see the alert lights illuminate on my dash! this can't be happening?, not now!. . I immediately hit my horn and avoid getting slammed into by vehicles behind me. I slowly creep on my last battery line onto the righthand shoulder. My Prius died. I called Toyotas' (rap>roadside assistance program) and a tow truck was sent. I broke down in DC and (toyotas' rap) only takes me 50miles from the breakdown. I live 62 miles away! this is not acceptable! I was towed to springfield Toyotan and it was closed! (it is now 2130hrs! and I'm still not at the hospital and I'm in tears!) the tow truck driver was nice enough to tell me to call my insurance CO. I did and they sent another tow truck to pick me up. It is now 2230hrs! I still don't know the status of my daughter! the tow truck brings me to fredericksburg but to a Nissan dealership, it seems the address was wrong. We figured out that Toyota pohanka was down the street and the tow truck driver was considerate enough to bring me there. I had to drop off the vehicle and lucky I had someone pick me up to bring me home. Toyota pohanka of fredericksburg called me the next day and said they found error code p3191 referred to the TSB and reprogrammed the engine ecm per instructions.