This Preliminary Information communication provides information to the technician on the steps to diagnose and repair vehicles that engine overheating, and/or poor heater performance, AC off message, and Malfunction Indicator Lamp illumination. Technician will find Diagnostic Trouble Code P00B7 and/or P2181. Technician will gain access to the water outlet assembly and inspect for flashing or debris. If flashing or debris found in the water outlet assembly it will need to be replaced. Also inspect the upper heater core hose and coolant bypass pipe at the water outlet for a black plug. If plug is found, remove and discard.