A/T System Description - Electronic Control System

Electronic Control System


Functional Diagram

The electronic control system consists of the Powertrain Control Module (PCM), sensors, 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, clutch pressure control, and lock-up control is stored in the PCM.
The PCM switches the shift solenoid valves and the A/T clutch pressure control solenoid valves on hydraulic control to control shifting transmission gears and lock-up torque converter clutch.

 

Electronic Control System (cont'd)


Electronic Controls Location


NOTE: The illustrations shows LHD model; RHD model is similar.

 

 

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, B, C, and E to control shifting.

Also, a Grade Logic Control System has been adopted to control shifting in [D] position. 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, and the shift lever position signal, to control shifting while vehicle is ascending or descending a slope.

 

Electronic Control System (cont'd)


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

Position Gear position Shift solenoid valves 
[D] Shifting from [N] position OFF ON ON OFF 
Stays in 1st ON ON ON OFF 
Shifting gears between 1st and 2nd OFF ON ON OFF 
Stays in 2nd OFF ON OFF OFF 
Shifting gears between 2nd and 3rd OFF ON ON OFF 
Stays in 3rd OFF OFF ON OFF 
Shifting gears between 3rd and 4th OFF OFF OFF OFF 
Stays in 4th ON OFF OFF OFF 
[2] 2nd gear OFF ON OFF OFF 
[1] 1st gear ON ON ON OFF 
[R] Shifting from [P] and [N] position OFF ON OFF ON 
Stays in reverse ON ON OFF ON 
Reverse inhibitor control OFF OFF ON OFF 
[P] Park OFF ON OFF ON 
[N] Neutral OFF ON ON OFF 

Grade Logic Control


Ascending Control

When the PCM determines that the vehicle is climbing a hill in [D] position, the system extends the engagement area of 2nd, and 3rd gears 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 [D] position, the shift-up speed from 3rd to 4th gear, and from 2nd to 3rd gear (when the throttle is closed) becomes faster than the set speed for flat road driving to widen the 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 3rd gear driving areas, and 2nd gear driving areas according to the magnitude of a gradient stored in the PCM. When the vehicle is 4th gear, and you are decelerating when you are applying the brakes on a steep hill, the transmission will downshift to lower gear. When you accelerate, the transmission will then return to higher gear.

 

Electronic Control System (cont'd)


Clutch Pressure Control

The PCM actuates the A/T clutch pressure control solenoid valves A, B and C to control the clutch pressure. When shifting between lower and higher gears, the clutch pressure regulated by the A/T clutch pressure control solenoid valves A, B, and C engage and disengage the clutch smoothly.
The PCM inputs signals from the various sensors and switches, perform processing data, and outputs a current to the A/T clutch pressure control solenoid valves A, B, and C.

 

Lock-up Control

The shift solenoid valve E controls the hydraulic pressure to switch the lock-up shift valve and lock-up ON and OFF.
The PCM actuates the shift solenoid valve E and the A/T clutch pressure control solenoid valve A to control the torque converter clutch lock-up. When the shift solenoid valve E is turned ON, the condition of the lock-up starts.
The A/T clutch pressure control solenoid valve A regulates and apply the hydraulic pressure to the lock-up control valve to control the volume of the lock-up.
The lock-up mechanism operates in 3rd and 4th gears in [D] position, and 3rd gear in [D] position over-drive off mode.



 

Electronic Control System (cont'd)


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.

 


PCM CONNECTOR A (31P)
Terminal Number Wire Color Signal Description Measuring Conditions/Terminal Voltage 
A2 YEL/BLK IGP2 Power supply circuit from main relay With ignition switch ON (II): Battery voltage
With ignition switch OFF: 0 V 
A3 YEL/BLK IGP1 Power supply circuit from main relay With ignition switch ON (II): Battery voltage
With ignition switch OFF: 0 V 
A4 BLK PG2 Ground  
A5 BLK PG1 Ground  
A10 GRN/YEL SG2 Sensor ground  
A11 GRN/WHT SG1 Sensor ground  
A20 YEL/BLU VCC2 Power supply circuit for sensors With ignition switch ON (II): About 5 V
With ignition switch OFF: 0 V 
A21 YEL/RED VCC1 Power supply circuit for sensors With ignition switch ON (II): About 5 V
With ignition switch OFF: 0 V 
A23 BRN/YEL LG2 Ground  
A24 BRN/YEL LG1 Ground  


PCM CONNECTOR B (24P)
Terminal Number Wire Color Signal Description Measuring Condition/Terminal Voltage 
B14 RED/BLK LS A+ A/T clutch pressure control solenoid valve A power supply positive electrode With ignition switch ON (II): Pulsing signal 
B16 BRN/WHT LS B+ A/T clutch pressure control solenoid valve B power supply positive electrode With ignition switch ON (II): Pulsing signal 
B24 BLU/YEL LS C+ A/T clutch pressure control solenoid valve C power supply positive electrode With ignition switch ON (II): Pulsing signal 

Electronic Control System (cont'd)


PCM Inputs and Outputs (cont'd)

 



PCM CONNECTOR C (22P)
Terminal Number Wire Color Signal Description Measuring Condition/Terminal Voltage 
C1 WHT/BLK LS A- A/T clutch pressure control solenoid valve A power supply negative electrode With ignition switch ON (II): 0 V 
C2 GRN SH C Shift solenoid valve C control Battery voltage in these positions:
  • [N] and [1]
  • 1st and 3rd gears in [D]
0 V in these positions:
  • [2], [P] and [R]
  • 2nd and 4th gears in [D]
 
C3 YEL SH E Shift solenoid valve E control Battery voltage in these positions:
  • [P] and [R]
0 V in these positions:
  • [N], [D], [2], and [1]
 
C4 GRN/WHT SH B Shift solenoid valve B control Battery voltage in these positions:
  • [2], [1], [P], [R], and [N]
  • 1st and 2nd gears in [D]
0 V in these positions:
  • 3rd and 4th gears in [D]
 
C6 BLU/BLK SH A Shift solenoid valve A control Battery voltage in these positions:
  • [R] and [1]
  • 1st and 4th gears in [D]
0 V in these positions:
  • [2], [P] and [N]
  • 2nd and 3rd gears in [D]
 
C7 WHT/RED NM Mainshaft speed sensor input With ignition switch ON (II): 0 V or about 5 V
With engine at idle in [N] position:
1.5 V-3.5V 


PCM CONNECTOR C (22P)
Terminal Number Wire Color Signal Description Measuring Condition/Terminal Voltage 
C8 BLK/RED LS B- A/T clutch pressure control solenoid valve B power supply negative electrode With ignition switch ON (II): 0 V 
C10 BLU/WHT OP3SW 3rd clutch pressure switch signal input With ignition switch ON (II): About 5 V
(No 3rd clutch pressure)
With 3rd clutch pressure: About 0 V 
C11 GRN/RED ATP 2 Transmission range switch [2] position signal input In [2] position: 0 V
In other than [2] position: About 5 V 
C12 RED/WHT ATP RVS Transmission range switch RVS ([R] position) signal input In [R] position: 0 V
In other than [R] position: About 5 V 
C13 BLU/RED OP2SW 2nd clutch pressure switch signal input With ignition switch ON (II): About 5 V
(No 2nd clutch pressure)
With 2nd clutch pressure: About 0 V 
C14 RED/YEL TATF ATF temperature sensor signal input With ignition switch ON (II): 0.2 V-4.8 V
With ignition switch OFF: 0 V 
C15 BLU NC Countershaft speed sensor input With ignition switch ON (II): 0V or about 5 V
With driving: About 1.5 V-3.5 V 
C16 WHT/BLU LS C- A/T clutch pressure control solenoid valve C power supply negative electrode With ignition switch ON (II): 0 V 
C19 BRN ATP 1 Transmission range switch [1] position signal input In [1] position: 0 V
In other than [1] position: About 5 V 


PCM CONNECTOR D (17P)
Terminal Number Wire Color Signal Description Measuring Condition/Terminal Voltage 
D2 GRN O/D SW Over-drive (O/D) switch signal input With ignition switch ON (II): About 5 V
With ignition switch ON (II) and O/D switch ON: 0 V 
D4 BLK/RED ATP N Transmission range switch [N] position signal input In [N] position: 0 V
In other than [N] position: About 5 V 
D5 WHT ATP R Transmission range switch [R] position signal input In [R] position: 0 V
In other than [R] position: About 5 V 
D6 BLU/BLK ATP P Transmission range switch [P] position signal input In [P] position: 0 V
In other than [P] position: About 5 V 
D10 WHT/GRN ATP D Transmission range switch [D] position signal input In [D] position: 0 V
In other than [D] position: About 5 V 

Electronic Control System (cont'd)


PCM Inputs and Outputs (cont'd)

 


PCM CONNECTOR E (20P)
Terminal Number Wire Color Signal Description Measuring Conditions/Terminal Voltage 
E7 RED/YEL MRLY Power supply circuit from main relay 1 With ignition switch ON (II): 0 V
With ignition switch OFF: Battery voltage 
E9 YEL/BLK IG1 Power supply circuit for solenoid valves With ignition switch ON (II): Battery voltage
With ignition switch OFF: 0 V 
E13 WHT/BLU SLC Shift lock control With ignition switch ON (II), brake pedal pressed, and accelerator pedal released: About 5 V 
E22 WHT/BLK BK SW Brake pedal position switch signal input Brake pedal pressed: Battery voltage
Brake pedal released: 0 V 
E23 LT BLU K-LINE Communication line PCM-to-DLC With ignition switch ON (II): Battery voltage 
E24 YEL SEFMJ Multiplex line PCM-to-gauge assembly With ignition switch ON (II): About 5 V 
E29 BRN SCS SCS terminal on the DLC signal input With ignition switch ON (II)
  • SCS terminals on the DLC open: About 5 V or battery voltage
  • SCS terminals short-circuited to ground: 0 V