TSB: Some 2016 ? 2019 model year Prius and 2017 ? 2019 model year Prius Prime vehicles may exhibit one or more of the following conditions due to a coolant leakage at the front exhaust pipe heat exchanger: ? Low coolant level ? MIL ON accompanied by Diagnostic Trouble Code (DTC) P148F00 ? Poor heater performance The front exhaust pipe with heat exchanger assembly has been updated. Follow the Repair Procedure in this bulletin to address this condition.