DTC P0666; Ecu Internal Temperature Sensor Circuit Malfunction: Notes

WARNING: This page is about a different car, the 2017 Mazda 3. However, it is still accessible from the selected car via links, so may be relevant.

DETECTION CONDITION & POSSIBLE CAUSE

DTC P0666:00
DETECTION CONDITION	Under the following condition, there is malfunction in circuit of ECU internal temperature sensor: Battery voltage is 8 V or more.
FAIL-SAFE FUNCTION	Inhibits learning control. Inhibits neutral idle control.
POSSIBLE CAUSE	Control valve body malfunction ECU internal temperature sensor (built-into TCM) malfunction
SYSTEM WIRING DIAGRAM	Not applicable