Electronic Control System

Functional Diagram





The electronic control system consists of the transmission control module (TCM), sensors, switches, and solenoid valves. Shifting is electronically controlled for comfortable driving under all conditions.
The TCM inputs signals from the ECM, sensors and switches, perform processing data, and outputs signals for automatic transmission control system. The A/T control system includes the shift control, pulley pressure control, start clutch pressure control, reverse inhibitor control, and creep aid control, is stored in the TCM. The TCM actuates the pulley control solenoids to control the pulley control valves A and B shifting transmission pulley ratios.





Electronic Controls Location

Pulley Pressure Control/Shift Control





To reduce belt slippage and increase belt life, the TCM calculates signals from the sensors and switches, and actuates the pulley pressure control solenoid valves to maintain optimum pulley pressure. When the pulley ratio is low (low vehicle speed), high hydraulic pressure works on the movable face of the driven pulley and reduces the effective diameter of the driven pulley, and a lower hydraulic pressure works on the movable face of the drive pulley to eliminate the steel belt slippage. When the pulley ratio is high (high vehicle speed), high hydraulic pressure works on the movable face of the drive pulley and reduces the effective diameter of the drive pulley, and a lower hydraulic pressure works on the movable face of the driven pulley to eliminate the steel belt slippage.
The TCM compares actual driving conditions with memorized driving conditions to control shifting, and it instantly determines a drive pulley ratio from various signals sent from sensors and switches. The TCM activates the CVT drive pulley pressure control valve to control pulley pressure to the pulleys. The drive pulley drives the driven pulley via a steel belt at varying ratios ranging from 2.367 to 0.407 in the [D] position.

Start Clutch Pressure Control





The hydraulic-controlled start clutch controls smooth starting-off and creeping in the [D], [S], [L], and [R] positions like a torque converter. The TCM inputs signals from the ECM, sensors, and switches, and actuates the start clutch pressure control valve to regulate the clutch reducing pressure, and the clutch reducing pressure controls the start clutch.

Creep Aid Control System





The Creep Aid Control System keeps the brakes applied during auto idle stop. This prevents the vehicle from rolling forward or backward between the time the driver releases the brake pedal (to press the accelerator pedal) and the engine starts, engaging the start clutch.
When the vehicle comes to a stop in auto idle stop, the TCM turns the creep-aid system solenoid valves A and B ON. This maintains the brake pressure that was applied during the stop. Since there is no hydraulic pressure to engage the start clutch, this helps keep the vehicle from moving forward or rearward when the driver moves his/her foot from the brake pedal to the accelerator pedal. The instant the brake pedal is released, the engine auto-starts.





When the engine auto-starts, the ATF pump builds up enough pressure for the start clutch to engage. The TCM turns creep-aid system solenoid valves A and B OFF, when certain parameters are met, releasing the brakes.





TCM Electrical Connection

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TCM Inputs and Outputs





TCM CONNECTOR B (24P)

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TCM CONNECTOR C (17P)