DTC Advanced Diagnostics: P1A4B: General Description

When the transmission control module (TCM) shifting control malfunctions, it may cause unintended rapid deceleration, caused by the lock-up of the countershaft. The lock-up of the countershaft may occur by a cause of abnormal engagement combinations of the clutches and the brakes or abnormal switching of the two-way clutch. The TCM monitors the conditions of the clutch, the brake, and the two-way clutch to secure safety before the vehicle leads to unintended rapid deceleration. The TCM presumes that there is abnormal engagement of the clutches and the brakes or an abnormal switching of the two-way clutch from the values of the transmission fluid pressure sensor and the two-way clutch actuator valve stroke sensor. If the TCM determines a shifting control malfunction, a DTC is stored.

Monitor Execution, Sequence, Duration, DTC Type