My new to me (3.5 weeks) 02 WRX with 28K miles is at the dealer as we speak getting a new battery (under warranty) after it would not start yesterday with our single digit N.E. PA temps. I have had weeks of an occasional "check engine" light on startup, that would go out on a restart, and was probably due to same. The motor would turn over for a while but not start, until jumped. It does take a certain amount of juice to turn AND fire the motor.