I have a 2003 HCH and the IMA light came on, followed by the check engine light a few weeks later.

This seems to be common, especially at this age/mileage (88K)

I took it to a dealer, but I have moved, so this is a new dealer to me, and I'm out in the sticks...and their diagnistics said, "The battery wasn't holding charge, and I wasn't getting Assist. I needed a new battery."

MPG is definitely down, so maybe.

BUT, I did use the rear defrost a few days ago, and that worked fine...plus the battery monitor went down like usual. This is how it has always worked for me.

So, is the battery really shot? If it powered the defrost, behaving as usual...could it be somethng else in the IMA?