Dan -

My '97 Turbo does the same thing intermittently when the humidity is high. I live in SC, so that pretty much covers the summer. Have discussed it a few times with my mechanic. His best advice (and it's worked for three years now) is to check the freon twice a summer. No leaks so far. As long as the freon checks out, I simply ignore it. I've even cleared the fault by disconnecting the battery for a few minutes. No flashes for a few days until the humidity spikes.

If it continues even in low humidity period, it may warrant further checking.

He pulled some codes for me two summers ago. I can't remember what he got, but upon review, they were general an non-conclusive.

My (and my mechanic's) only assumption is that the Swedes just weren't anticipating a Southern summer. :)

Please post if you discover anything specific.
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1997 850 T-5 (Chip, exhaust, suspension upgraded)