How does ECU know if Manual or Automatic Transmission is Used (Page 3/3) Romsk DEC 29, 11:42 PM Patrick, Thanks... it's a fun project. Mickey_Moose, Thanks for the schematics, they are very helpful. I have no idea how you found schematics, but I am glad you did. They make good sense to me. The CALPACK looks like a custom chip... I think mainly because it is the backup/limp home circuitry in case other circuitry fails. I noticed that the pages seem to from two ECUs... not everything lines up. GM, go figure.