Gear Lockout: Description and Operation

How the Circuit Works
With the ignition switch in ON (II) or START (III), battery voltage is supplied through fuse 6 (of the under-dash fuse/relay box) to the reverse lockout solenoid. The vehicle speed sensor (VSS) provides a vehicle speed signal to the engine control module (ECM). When the speed is above 12 mph (20 km/h), the ECM grounds the reverse lockout solenoid, which pushes the select lock cam into the locked position, keeping you from shifting into reverse. When the vehicle speed is below 9 mph (15 km/h) the ECM ground is removed, de-energizing the reverse lockout solenoid, the select lock return spring pulls the select lock cam back, enabling you to shift into reverse.