I've never replied to such an old post, but had to because it's sooo.... GOOD! Thank you for explaining the backwards Volvo thinking for both naming it an overdrive, and for having it powered when in 4th gear - which does sound crazy. I just repaired the frayed/destroyed/shorting white wire from the unit on my 240, and it works fine now (hard as hell to get to, but... persistence...), but I also have the bypass from IPD as a future back-up, when needed, and an extra relay if that's a future problem. Nice to confirm that just removing the wiring would NOT have helped - would have kept in 3rd gear forever. Thanks for the great post.