Some customers may complain about poor heater performance even after the engine reaches normal operating temperature. This may be caused by a plugged heater core. For 2014-2016 Mazda6 and 2013-2016 (US spec) / 2017 (Mexico spec) CX-5, the CHECK ENGINE light
may turn on with DTC P011A:00 (ECT sensor No.1/No.2 performance problem) stored at the same time. NOTE: Refer to TSB 01-015/15 if the customer is using a block heater at temperatures below freezing. To solve this concern, two mass production changes have been
implemented. a) The concentration of the coolant has been increased so that the amount of the contained anti-rust additive is higher. b) The composition of the coolant has been changed (the ratio of the anti-rust additive has increased).
