Jeff, I think you can use the cruise signal or the VSS signal to the ecm. The C1500 updates after 16 mph, at worst with a 2000 PPM signal, it would update at 32 mph. AL -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.diy-efi.org/pipermail/gmecm/attachments/20010119/f61362c7/attachment.html>