Try disconnecting the neg and positive in the trunk. I've heard people also touching the wires together, and leaving them like that for 30 min. (That's actually the instructions for Audi / VW) I did this on my car the other day, when I was having problems with the GT1. That reset everything. Which was a pain in the ass as I had to reprogram all the crap that's in the car. Bluetooth, radio, seat memory, time, all mpg reset, I mean everything.

Otherwise, I think you might have to get someone with a GT1 to clear it, or similar computer.