I know this has been discussed previously, but I'd like to get a second opinion on my particular situation. Car is a 2005 Prius with 66000 miles. One hot day (100F) about three weeks ago the brake warning light combination came on (brake, brake warning, ABS, VSC) at 30mph, not triggered by any harsh braking. Braking was normal. We took it to the local Toyota dealer who checked for any stored codes but found none. Their diagnosis, from their research, was a possible skid control ECU failure. They reset the warnings and said that if it happened again we should go back to have the ECU replaced (~$2000) but they didn't want us to incur that expense without further proof that something was wrong. It has recurred and now seems to follow a pattern. When we set out for the first time everything is OK with no warnings. We drive a few miles and then stop and turn off the engine (e.g. for an errand). When we restart, the warning lights appear and stay on. Next day, same pattern happens again. Braking seems normal when lights are on. I'd probably rule out a loose connection as the pattern is repeatable although the intermittent nature of the problem is puzzling. We wondered if the problem might be somehow related to heat. Is this possibly a 12V battery issue? The battery has never been changed. After a couple of days without using the car I ran the built-in self test procedure and it was a little low. (12.1V unloaded, 11.8V loaded, 14.4-14.5V charging). The dealer tested the battery when we took the car in and marked it as passed. We haven't noticed any other obvious electrical problems. Since ECU failures are rare I'm inclined to change the battery next before replacing the ECU. And I'd hate to replace the ECU and find the problem is still there. Any other suggestions?