TSB: Mazda Refrigerant Pressure Sensor

This bulletin applies to 2024-2025 Mazda CX-90 PHEV and 2025 CX-70 PHEV vehicles built before March 1, 2025. Some vehicles may exhibit a check engine light on at engine startup, with DTC P0531:00 (refrigerant pressure sensor No. 1 system, function malfunction) stored in memory.

This is caused by improper control logic of the PCM and the dash-electrical supply unit (Dash-ESU). To eliminate the concern, the control logic has been modified. Reprogram the PCM and Dash-ESU with the Mazda modular diagnostic system (M-MDS), using Mazda diagnostic and repair software (MDARS).