Tod Control System

TOD position usually drives rear wheels and transmits torque to front wheels with help of electronically controlled torque split mechanism according to running conditions encountered. Driving force is directly transmitted to rear wheels. This force is split by transfer case and delivered to front wheels.

Magnitude of torque transmitted to front wheels is controlled by changing pressing force of electromagnetic multi-plate disc clutch built into transfer unit. Pressing force of clutch is controlled by changing voltage to electromagnetic coil mounted to rear of clutch. When clutch is completely disengaged, rear wheels are driven. When clutch is completely engaged, a rigid four wheel drive mode is obtained.

Torque split status is controlled continuously between rear wheel and four wheel drive modes. System includes front and rear speed sensors and throttle position sensor which monitors engine output. ECU receives signals from sensors and changes pressing force of electromagnetic multi-plate disc clutch to determine torque distribution on front and rear wheels.

When slip of rear wheels is increased against current torque level in normal rear wheel drive mode, ECU detects slip condition, determines optimum torque based on feedback control logic, and increases torque to front wheels.

ECU uses signal from throttle position sensor to predict future vehicle condition and intention of driver with respect to acceleration and deceleration, and determines initial torque distribution using this data and information from wheel speed sensors.

A TOD indicator, located on instrument panel, informs driver of current transfer unit status. Indicator will display drive mode (2H, TOD or 4L) and torque split status. Indicator is also used to display Diagnostic Trouble Codes (DTC).