Shift Interlock: Description and Operation

Automatic Transmission Shift Lock Control System
The automatic transmission shift lock control system is a safety device that prevents an inadvertent shift out of PARK when the engine is running. The driver must press the brake pedal before moving the shift lever out of the PARK position. The system consists of the following components.
^ The park relay
^ The automatic transmission shift lock control solenoid
^ The automatic transmission shift lock control switch
^ The Rear Integration Module (RIM)
^ The Powertrain Control Module (PCM)
With the ignition ON, positive voltage is supplied from the ignition switch to the coil side feed circuit of the park relay. The RIM receives a gear position input signal from the PCM through a class 2 serial data message. When the RIM receives a PARK position message from the PCM, the RIM applies a ground to the control circuit of the park relay. This energizes the relay, closing the switch contacts, battery voltage flows through the relay to the automatic transmission shift lock control switch. With the brake pedal released voltage flows through the normally closed contacts of the automatic transmission shift lock control switch to the automatic transmission shift lock control solenoid. The automatic transmission shift lock control solenoid is permanently grounded. This energizes the automatic transmission shift lock control solenoid and mechanically locks the shift lever in the PARK position. When the driver presses the brake pedal the contacts of the automatic transmission shift lock control switch open, de-energizing the automatic transmission shift lock control solenoid. This allows the shift lever to be moved from the PARK position.

When the shift lever is moved out of the PARK position, the PCM sends a class 2 serial data message to the RIM. The RIM opens the ground path of the park relay control circuit, de-energizing the park relay and disabling the automatic transmission shift lock control solenoid. Once the vehicle is out of PARK, the automatic transmission shift lock control solenoid remains de-energized until the RIM receives a PARK signal from the PCM.

Reverse Lockout Control
The reverse lockout system is a safety device that prevents an inadvertent shift from a forward or neutral gear into reverse. The system consists of the following components.
^ The reverse lockout solenoid
^ The Dash Integration Module (DIM)
When the ignition switch is turned ON, battery voltage is supplied to the feed circuit of the reverse lockout solenoid. The DIM supplies the ground for the control side circuit. When the DIM determines that the ignition is ON and the vehicle has been traveling at over 8 kph (5 mph) for 15 seconds or longer, it grounds the control circuit of the reverse lockout solenoid. This energizes the reverse lockout solenoid and mechanically prevents the shift lever from being moved into the REVERSE position.