[brcidd]

I've seen my scan tool not allow an engine to even crank- unplug it and it cranks and starts- saw it on a '97 U-van and just saw it last week on 2004 Lesabre...have seen it cause instrument clusters to go wild on Chryslers and Jeeps- speedometers flutter, gas guage goofy- unplug scan tool and all is fine.

So it has to do with data line and communications- doesn't always happen. I remember wasting 2 or 3 hours dubugging why a Pontiac Transport would not crank- when finally, I unplug scan tool and it starts right up...WTF....You never forget to unplug the tool first, now.....