DTC P0638-00: Throttle Valve Actuator Control Range/Performance Problem: Outline

WARNING: This page is about a different car, the 2020 Mazda CX-30. However, it is still accessible from the selected car via links, so may be relevant.

DTC P0638:00 (PCM, SKYACTIV-G) DETECTION CONDITION AND POSSIBLE CAUSE

System malfunction location	Throttle valve actuator control range/performance problem
Detection condition	The PCM compares the actual TP with the target TP. If the difference is more than the threshold value, the PCM determines that there is a throttle valve actuator control range/performance problem.
Fail-safe	Restricts the upper limit of the engine speed. Fixes the throttle valve opening angle.
Possible cause	Throttle body connector or terminals malfunction Short to ground in throttle valve actuator control circuit PCM connector or terminals malfunction Short to power supply in throttle valve actuator control circuit Open circuit in throttle valve actuator control circuit Throttle valve actuator malfunction Throttle valve malfunction PCM malfunction
Courtesy of MAZDA MOTORS CORP.