First, thanks for a great site. I spend hours just reading. I have a 1990 IROC-Z, with the five speed. When I got the car it would not start. The VATs system was not working. I have a chip burned with out the VATs and the car now runs. I am getting and SES light. So I go get my trusty old AutoXray scanner and hock it up. It says that it can not communicate. I try a few time with no luck. So I us a universal tool (paper clip) and the fans kick on and the ECM starts flashing code 24 (but the speedometer works). Any one know why I can't scan and why code 24 with a working speedometer?

Thanks so much.

Dave