This Preliminary Information communication provides information to the technician with information about vehicles that misfires or roughness on cold start up. Technician may find Diagnostic Trouble Code P0300 set. Technician will need to add coolant dye to the system and run the engine through warm up to circulate the dye. Pressurize the cooling system after a cold soak and inspect the cylinder with a bore scope for coolant dye. If coolant is found in the cylinder technician will need to contact General Motors Product Quality Center for engine replacement.
