A/T System Description - Electronic Control System
A/T System Description - Electronic Control System
Electronic Control System
Functional Diagram
The electronic control system consists of the PCM, the sensors, and the solenoid valves.
Shifting and lock-up are electronically controlled for comfortable driving under all conditions.
The PCM receives input signals from the sensors, switches, and other control units, processes data, and outputs signals for the engine control system and the A/T control system. The A/T control system includes shift control, grade logic control, clutch pressure control, and lock-up control.
The PCM switches the shift solenoid valves and the A/T clutch pressure control solenoid valves on and off to control shifting the transmission gears and the torque converter lock-up.
Shift Control
The PCM instantly determines which gear should be selected by various signals sent from the sensors and the switches, and it actuates shift solenoid valves A, B, C, D, and E to control gear selection.
The shift solenoid valves are a normally closed type valves. The shift solenoid valve opens the port of the shift solenoid valve pressure leading to the shift valves, while the shift solenoid valve is turned ON by the PCM, and closes the port when the shift solenoid valve is OFF.
The combination of driving signals to shift solenoid valves A, B, C, D, and E are shown in the table.
Shift Control - Grade Logic Control
The grade logic control system is used to control shifting in D. The PCM compares actual driving conditions with programmed driving conditions, based on input from the accelerator pedal position sensor, the throttle position sensor, the engine coolant temperature sensor, the barometric pressure sensor, the brake pedal position switch signal, and the shift lever position signal, to improve shifting control while the vehicle is ascending or descending a slope.
Grade Logic Control: Ascending Control
When the PCM determines that the vehicle is climbing a hill in D, the system extends the engagement area of 2nd, 3rd, and 4th gears to prevent the transmission from frequently shifting between 2nd and 3rd gears, between 3rd and 4th gears, and between 4th and 5th gears, so the vehicle can run smoothly, and have more power when needed.
NOTE: Shift commands stored in the PCM between 2nd and 3rd gears, between 3rd and 4th gears, and between 4th and 5th gears, enable the PCM to automatically select the most suitable gear based on the steepness of the grade.
Grade Logic Control: Descending Control
When the PCM determines that the vehicle is going down a hill in D, the upshift speed from 4th to 5th gear, from 3rd to 4th gear, and from 2nd to 3rd gear (when the throttle is closed) becomes higher than the set speed for flat road driving to extend 4th gear, 3rd gear, and 2nd gear driving area. This, in combination with engine braking from the deceleration lock-up, achieves smooth driving when the vehicle is descending. There are three descending modes with different 4th gear driving areas, 3rd gear driving areas, and 2nd gear driving areas based on the steepness of the grade stored in the PCM. When the vehicle is in 5th gear or 4th gear, and the vehicle is decelerating while applying the brakes on a steep hill, the transmission downshifts to a lower gear. When you accelerate, the transmission then returns to a higher gear.
Shift Control - D Position D3 Driving Mode Control
The automatic transmission is provided with the D3 driving mode in D. D has two modes; general driving mode (shifts gears automatically 1st through 5th), and the D3 driving mode (shifts gears automatically 1st through 3rd). The transmission mode switches by pressing the D3 button on the shift lever knob in D.
In D3 driving mode, the D3 indicator next to the D indicator in the gauge control module comes on. The D3 driving mode is cancelled by pressing the D3 button, and the D3 indicator goes off. Also, the D3 driving mode is cancelled when the ignition switch is turned to LOCK (0). When the shift lever is moved out of D in the D3 driving mode, the D3 indicator goes off, but the transmission returns into the D3 driving mode when returning the shift lever into D, and the D3 indicator comes on.
Clutch Pressure Control
The PCM actuates A/T clutch pressure control solenoid valves A, B, and C to control the clutch pressure. When shifting between gears, the clutch pressure regulated by A/T clutch pressure control solenoid valves A, B, and C engages and disengages the clutch smoothly.
The PCM receives input signals from the various sensors, switches, processes the data, and outputs current to A/T clutch pressure control solenoid valves A, B, and C.
Lock-up Control
Shift solenoid valve E controls the hydraulic pressure to switch the lock-up shift valve and lock-up ON and OFF. When the PCM actuates shift solenoid valve E and A/T clutch pressure control solenoid valve A ON, and lock-up starts. A/T clutch pressure control solenoid valve A regulates and applies hydraulic pressure to the lock-up control valve to control the amount of lock-up.
The lock-up mechanism operates in D (2nd, 3rd, 4th, and 5th), and in D in the D3 driving mode (2nd and 3rd).
Self-diagnosis
If the PCM detects the failure of a signal from a sensor, a switch, a solenoid valve, or from another control unit, it stores Pending or Confirmed DTCs. Depending on the failure, a Confirmed DTC is stored in either the first or the second drive cycle. When a DTC is stored, the PCM blinks the D indicator and/or turns on the malfunction indicator lamp (MIL) by a signal sent to the gauge control module via F-CAN.
- One Drive Cycle Detection Method
When an abnormality occurs in the signal from a sensor, a switch, a solenoid valve, or from another control unit, the PCM stores Pending or Confirmed DTCs for the failure and blinks the D indicator and/or turns on the MIL immediately.
- Two Drive Cycle Detection Method
When an abnormality occurs in the signal from a sensor, a switch, a solenoid valve, or from another control unit in the first drive cycle, the PCM stores a Pending DTC. The D indicator and the MIL do not turns on at this time. If the failure continues in the second drive cycle, the PCM stores Pending or Confirmed DTCs and blinks the D indicator and/or turns on the MIL.
Fail-safe Function
When an abnormality occurs in the signal from a sensor, a switch, a solenoid valve, or from another control unit, the PCM ignores that signal and substitutes a pre-programmed value for that signal to allow the automatic transmission to continue operating. This causes a DTC to be stored and the D indicator to blink and/or the MIL to come on. The transmission may not shift normally during fail-safe operation. Do not run the test driving diagnosis when the MIL is ON, or the D indicator is blinking.
Shift Lock Control
The shift lock system prevents the shift lever from mis-shifting. The shift lock solenoid is normally OFF. After starting the engine in P, the shift lever cannot move to any other position from P because the shift lock stop stops the lock pin unless certain conditions are met. When the brake pedal is pressed and the accelerator pedal is not pressed, the PCM commands the shift lock solenoid is ON; the shift lock solenoid plunger in the shift lock solenoid pulls the shift lock stop to release the lock pin. Pressing the shift lever button allows the shift lever to move to any other position. When the brake pedal and the accelerator pedal are pressed at the same time, the PCM commands the solenoid OFF and the shift lock system is locked.
When the shift lock system does not operate due to mechanical or electrical problem, you can unlock the shift lock temporarily by inserting the ignition key into the shift lock release hole and pressing the shift lock release. When the shift lock release end is pressed, the shift lock stop releases the lock pin, and the shift lever can move to any other position.
PCM A/T Control System Electrical Connections -
PCM A/T Control System Inputs and Outputs at PCM Connector A (square) (44P) (K24Z1 Engine)
PCM A/T Control System Inputs and Outputs at PCM Connector B (square) (44P) (K24Z1 Engine)
PCM A/T Control System Inputs and Outputs at PCM Connector B (square) (44P) (K24Z1 Engine)
PCM A/T Control System Inputs and Outputs at PCM Connector C (square) (44P) (K24Z1 Engine)
PCM A/T Control System Electrical Connections - K24Z6 Engine
PCM A/T Control System Inputs and Outputs at PCM Connector A (square) (49P) (K24Z6 Engine)
PCM A/T Control System Inputs and Outputs at PCM Connector B (square) (49P) (K24Z6 Engine)
PCM A/T Control System Inputs and Outputs at PCM Connector B (square) (49P) (K24Z6 Engine)
PCM A/T Control System Inputs and Outputs at PCM Connector C (square) (49P) (K24Z6 Engine)
