Reverse Inhibitor Control

When R is selected while the vehicle is moving forward, the PCM commands shift solenoid valve A to turn OFF, and E to remain OFF. Shift solenoid valve A pressure (SA) is not applied to shift valve A so that line pressure (3A) is not applied to the servo valve. Also shift solenoid valve E pressure (SE) is not applied to shift valve E so that line pressure (3') is not applied to the servo valve. The servo valve cannot be shifted to the reverse position, and hydraulic pressure is not applied to the 4th clutch from servo valve for reverse; as a result, power is not transmitted to the reverse direction.

Fig 1: Automatic Transmission Flow Diagram - Driving In Reverse Gear

Courtesy of AMERICAN HONDA MOTOR CO., INC.