Holding Off and Warmer in a Caddy will get you some info but won't work here Killer. If it is the way dsatt12 is talking with the GM 1 PCM with the OBD II connector I don't think there $100 scanner is going to help. OBD II codes are standardized for all manufacturers and the old code set is manufacturer specific. That's probably the read error problem. You might be able to disconnect the battery and kill the light. But if the problem is still there and you complete the PCM's drive cycle it will come back on.