My 2004 Prius suddenly getting very low mpg...

Hi all,

Here's my situation. I have an 04 Prius with just over 42,000 miles on it (my dad bought brand new and he only drove it to and from work). We took it on a trip to Minnesota (about 1200 miles round trip). On the way home the *exclamation point of death* and several other warning lights came on and the car slowed and died. When restarted it wouldn't go over 25-30 mph. We stopped at a hotel and in the morning started it again - the lights were still on - drove it around the parking lot a bit. The lights went off and car drove normally. We took a chance and drove it home. Everything seems back to normal except now the car gets REALLY low mpg - between 26 and 32 mpg. Prior to this incident I was getting anywhere from 41 to 46 year round (I live in Chicago). I hooked up a scanner to it and these are the codes I got:

B1421 (Solar sensor circuit - not worried about that as car was inside)
B1443 (Ait outlet control servo circuit)
C1241 (Low battery positive voltage)
C1378 (Brake control power supply, skid control ECU, or wiring harnes)
C2310 (Open or short circuit in battery, PCON fuse, trans control ECU, or wiring harness)
C2318 (Low voltage error, 12V battery, HEV fuse, IGCT relay or wiring harness)

So a bunch of these codes are pointing towards electrical issues... Wonderiing if any of you out there have seen this happen before and know what the fix might be? If my hybrid battery is failing will that cause low mpg? Also, the small battery in the back of the car was replaced about 2 years ago because the car sat undriven for awhile and killed it. Since then it has been my daily driver.

Any help or info would be appreciated...

Thanks!

 

Thanks for your quick replies... I will check the voltage on the 12V. Seems odd that a brand new Toyota battery, driven daily, would die out after 2 years and 20,000 miles. So, in your experience that could be the cause of poor fuel economy?