DTC P0638: Throttle Actuator Control Circuit Range/Performance Problem

WARNING: This page is about a different car, the 2004 Mazda RX-8. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: DTC P0638 Detection Condition & Possible Causes Chart

Courtesy of MAZDA MOTORS CORP.

Diagnostic Procedure

Fig 2: DTC P0638 Diagnostic Procedure Chart

Courtesy of MAZDA MOTORS CORP.