Electronic Control System

Electronic Control System

Functional Diagram





The electronic control system consists of the powertrain control module (PCM), sensors, switches, and solenoid valves.
Shifting and lock-up are electronically controlled for comfortable driving under all conditions.
The PCM inputs signals from the sensors, switches, and other control units, perform processing data, and outputs signals for engine control system and A/T control system. The A/T control system includes shift control, grade logic control, CPC control, and lock-up control is stored in the PCM.
The PCM switches the shift solenoid valves, AFT clutch pressure control solenoid valves, and torque converter clutch solenoid valve on hydraulic circuit to control shifting transmission gears and lock-up torque converter clutch.





Electronic Controls Location

Shift Control





The PCM instantly determines which gear should be selected by various signals sent from sensors and switches, and it actuates the shift solenoid valves A and B to control shifting.
Also, a Grade Logic Control System has been adopted to control shifting in the D and D3 positions. The PCM compares actual driving conditions with memorized driving conditions, based on the input from the throttle position sensor, the engine coolant temperature sensor, the barometric pressure sensor, the brake pedal position switch signal, cruise control signal, and the shift lever position signal, to control shifting while vehicle is ascending or descending a slope, or reducing speed.





The PCM turns the shift solenoid valves A and B ON and OFF to control shifting transmission gear. The combination of driving signals to shift solenoid valves A and B are shown in table below.

Grade Logic Control System

Ascending Control





When the PCM determines that the vehicle is climbing a hill in the D and D3 positions, the system extends the engagement area of 2nd and 3rd gear to prevent the transmission from frequently shifting between 2nd and 3rd gears, and between 3rd and 4th gears, so the vehicle can run smooth and have more power when needed.
Shift schedules stored in the PCM between 2nd and 3rd gears, and between 3rd and 4th gears, enable it to automatically select the most suitable gear according to the magnitude of a gradient.

Descending Control





When the PCM determines that the vehicle is going down a hill in the D and D3 positions, the shift-up speed from 3rd to 4th gear and from 2nd to 3rd (when the throttle is closed) becomes faster than the set speed for flat road driving to widen the 3rd gear and 2nd gear driving areas. This, in combination with engine braking from the deceleration lock-up, achieves smooth driving when the vehicle is descending. There are two descending modes with different 3rd gear driving areas and 2nd gear driving areas to suit the magnitude of the gradients stored in the PCM. When the vehicle is in 4th gear, and you are decelerating while applying the brakes on a steep hill, the transmission will downshift to 3rd gear. When you accelerate, the transmission will then return to higher gear.

Deceleration Control
When the vehicle goes around a corner and needs to decelerate first and then accelerate, the PCM sets the data for deceleration control to reduce the number of times the transmission shifts. When the vehicle is decelerating from speeds above 27 mph (43 km/h), the PCM shifts the transmission from 4th to 2nd earlier than normal to cope with upcoming acceleration.

CPC (Clutch Pressure Control}





The PCM actuates the A/T clutch pressure control solenoid valve A to control CPC pressure. When shifting between lower gear and upper gear, CPC pressure regulated by the A/T clutch pressure control solenoid valve A engages and disengages the clutches smoothly.
The PCM inputs signals from the various sensors, perform processing data, and outputs a current to the A/T clutch pressure control solenoid valve A.

Lock-up Control System





The torque converter clutch solenoid valve controls modulator pressure to switch the lock-up shift valve and lock-up ON and OFF. The PCM controls the torque converter clutch solenoid valve and the A/T clutch pressure control solenoid valve B. When the torque converter clutch solenoid valve is turned ON, the condition of the lock-up starts.
The A/T clutch pressure control solenoid valve B regulates A/T clutch pressure control solenoid B pressure, and apply pressure to the lock-up control valve and the lock-up timing valve. The lock-up control mechanism operates in 3rd and 4th gears in D position, and in 3rd gear in D3 position.





PCM Electrical Connections

PCM Inputs and Outputs





The PCM terminal voltage and measuring conditions are shown for the connector terminals that are related to the A/T control system. The other PCM terminal voltage and measuring conditions are described in Fuel and Emissions.





PCM CONNECTOR A (31P)





PCM CONNECTOR B (24P)





PCM CONNECTOR C (22P)

PCM Inputs and Outputs








PCM CONNECTOR E (31P)