Outline Of Diagnosis

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

Detect the malfunction of transmission secondary solenoid and hydraulic circuit (stuck to low pressure side).
Judge as NG, when the secondary pressure sensor value at P0867 detection is less than the predetermined value, and the secondary pressure sensor voltage value after the predetermined period of time has elapsed since IG OFF is within the predetermined range.