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 recieves input signals from the sensors, switches, and other control units, perform processing data, and outputs signals for the 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 to control shifting transmission gears and lock-up torque converter clutch.

 

Electronic Control System (cont'd)


Electronic Controls Location

 

 

Shift Control

The PCM instantly determines which gears should be selected by various signals sent from sensors and switches, and it actuates the shift solenoid valves A, B, C, D, and E to control shifting.

Also, a grade logic control system has been adopted to control shifting in the D position. The PCM compares actual driving conditions with memorized driving conditions, based on the input from the accelerator pedal 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 the vehicle is ascending or descending a slope.

 

Electronic Control System (cont'd)


D Position D3 Driving Mode Control

This automatic transmission is provided with the D3 driving mode in the D position. The D position 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 switches the mode with pushing the D3 switch on the shift lever end.

NOTE: The illustration shows the LHD model; RHD model is symmetrical.

 

The transmission switches into the D3 driving mode in the D position by pushing the D3 switch, the D3 indicator next to the D indicator in the gauge assembly comes on. In the D3 driving mode, D3 driving mode is cancelled by pushing the D3 switch, and the D3 indicator goes off. Also, the D3 driving mode is cancelled when the ignition switch is turned off. When the shift lever is moved out of the D position 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 the D position, and the D3 indicator comes on.

 

Shift Solenoid Valve ON-OFF Operation

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

Position Gear position Shift solenoid valves 
Shifting from N position OFF ON ON OFF OFF 
Stays in 1st ON ON ON OFF OFF 
Shifting gears between 1st and 2nd OFF ON ON OFF OFF 
Stays in 2nd OFF ON OFF ON OFF 
Shifting gears between 2nd and 3rd OFF ON ON ON OFF 
Stays in 3rd OFF OFF ON OFF OFF 
Shifting gears between 3rd and 4th OFF OFF OFF OFF OFF 
Stays in 4th ON OFF OFF OFF OFF 
Shifting gears between 4th and 5th ON OFF OFF ON OFF 
Stays in 5th ON OFF ON ON OFF 
2nd gear OFF ON OFF ON OFF 
1st gear ON ON ON OFF OFF 
Shifting from P and N position OFF ON OFF OFF ON 
Stays in reverse ON ON OFF OFF ON 
Reverse inhibit OFF OFF ON OFF OFF 
Park OFF ON OFF OFF ON 
Neutral OFF ON ON OFF OFF 

Electronic Control System (cont'd)


Grade Logic Control: Ascending Control

When the PCM determines that the vehicle is climbing a hill in the D position, 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 smooth and have more power when needed.

Shift schedules stored in the PCM between 2nd and 3rd gears, between 3rd and 4th gears, and between 4th and 5th gears, enable it to automatically select the most suitable gear according to the magnitude of a gradient.

 


Grade Logic Control: Descending Control

When the PCM determines that the vehicle is going down a hill in the D position, the shift-up speed from 4th to 5th gear, 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 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 according to the magnitude of a gradient stored in the PCM. When the vehicle is in 5th gear or 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 a higher gear.

 

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 engages and disengages the clutch smoothly.
The PCM receives input signals from the various sensors and switches, performs data processing, and outputs a current to the A/T clutch pressure control solenoid valves A, B, and C.

 

Electronic Control System (cont'd)


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 lock-up condition 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 amount of the lock-up. The lock-up mechanism operates in 2nd, 3rd, 4th, and 5th gears in the D position, and 2nd and 3rd gears in the D position D3 driving mode.

 

PCM Electrical Connections

 

Electronic Control System (cont'd)


PCM Inputs and Outputs

 

PCM CONNECTOR A (31P)
Terminal Number Wire Color Signal Description Measuring Conditions/Terminal Voltage 
A4 BLK PG2 Ground Less than 1.0 V at all times 
A5 BLK PG1 Ground Less than 1.0 V at all times 
A8 BRN/YEL LG2 Ground Less than 1.0 V at all times 
A9 BRN/YEL LG1 Ground Less than 1.0 V at all times 
A18 BLU NC Output shaft (countershaft) speed sensor signal input With ignition switch ON (II): 0 V or about 5 V
While driving: About 2.5 V 
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 GRN/YEL SG2 Sensor ground Less than 1.0 V at all times 
A24 GRN/WHT SG1 Sensor ground Less than 1.0 V at all times 

PCM CONNECTOR C (22P)
Terminal Number Wire Color Signal Description Measuring Condition/Terminal Voltage 
C1 RED/BLK LS A A/T clutch pressure control solenoid valve A control With ignition switch ON (II): Pulsing signal 
C2 GRN SH C Shift solenoid valve C control Battery voltage in these positions:
  • N and 1
  • 1st, 3rd, and 5th gears in D and D3
  • Reverse inhibit in R
0 V in these positions:
  • P, R, and 2
  • 2nd and 4th gears in D and D3
 
C3 YEL SH E Shift solenoid valve E control Battery voltage in these positions:
  • P and R
0 V in these positions:
  • Reverse inhibit in R
  • N, D, D3, 2, and 1
 
C4 GRN/WHT SH B Shift solenoid valve B control Battery voltage in these positions:
  • P, R, N, 2, and 1
  • 1st and 2nd gears in D and D3
0 V in these positions:
  • Reverse inhibit in R
  • 3rd, 4th, and 5th gears in D and D3
 
C5 GRN/RED SH D Shift solenoid valve D control Battery voltage in these positions:
  • 2
  • 2nd and 5th gears in D and D3
0 V in these positions:
  • Reverse inhibit in R
  • P, R, N, and 1
  • 1st, 3rd, and 4th gears in D and D3
 
C6 BLU/BLK SH A Shift solenoid valve A control Battery voltage in these positions:
  • R and 1
  • 1st, 4th, and 5th gears in D and D3
0 V in these positions:
  • Reverse inhibit in R
  • P, N, and 2
  • 2nd and 3rd gears in D and D3
 
C7 BLU/YEL LS C A/T clutch pressure control solenoid valve C control With ignition switch ON (II): Pulsing signal 
C9 BRN ATP 1 Transmission range switch 1 position signal input In the 1 position: 0 V
In other than the 1 position: Battery voltage 
C10 BLU/WHT OP3SW 3rd clutch transmission fluid pressure switch signal input With ignition switch ON (II): About 5 V
With 3rd clutch pressure: 0 V 
C11 GRN/RED ATP 2 Transmission range switch 2 position signal input In the 2 position: 0 V
In other than the 2 position: Battery voltage 
C12 RED/WHT ATP RVS Transmission range switch RVS (R position) signal input In R position: 0 V
In other than the R position: Battery voltage 
C13 BLU/RED OP2SW 2nd clutch transmission fluid pressure switch signal input With ignition switch ON (II): About 5 V
With 2nd clutch pressure: 0 V 
C14 RED/YEL ATFT ATF temperature sensor signal input With ignition switch ON (II): 0.2 V-4.8 V
With ignition switch OFF: 0 V 
C15 BRN/WHT LS B A/T clutch pressure control solenoid valve B control With ignition switch ON (II): Pulsing signal 
C17 YEL ATP D Transmission range switch D position signal input In the D position: 0 V
In other than the D position: Battery voltage 
C18 YEL/RED ATP FWD Transmission range switch D, D3, and 2 position signals input In the D, D3, and 2 positions: 0 V
In other than the D, D3, and 2 positions: Battery voltage 
C19 WHT/RED NM Input shaft (mainshaft) speed sensor signal input With ignition switch ON (II): 0 V or about 5 V
With engine at idling in N position: About 2.5 V 
C20 RED/BLK ATP N Transmission range switch N position signal input In the N position: 0 V
In other than the N position: Battery voltage 

Electronic Control System (cont'd)


PCM Inputs and Outputs (cont'd)

 

PCM CONNECTOR D (17P)
Terminal Number Wire Color Signal Description Measuring Conditions/Terminal Voltage 
D2 YEL/BLU P-PIN SW Park pin switch signal input With ignition switch ON (II): About 5 V 
D3 GRN D3 SW D3 switch signal input With ignition switch ON (II): Battery voltage 
D5 WHT ATP R Transmission range switch R position input In the R position: 0 V
In other than the R position: Battery voltage 
D6 BLU/BLK ATP P Transmission range switch P position input In the P position: 0 V
In other than the P position: Battery voltage 

PCM CONNECTOR E (31P)
Terminal Number Wire Color Signal Description Measuring Conditions/Terminal Voltage 
E2 YEL/BLK SLC Shift lock solenoid control
(ground side) 
With ignition switch ON (II), in the P position, brake pedal pressed, and accelerator released: 0 V 
E9 BLK/YEL IG1 Power supply circuit for solenoid valves With ignition switch ON (II): Battery voltage
With ignition switch OFF: 0 V 
E13 YEL SEFMJ Communication line PCM-to-gauge control module With ignition switch ON (II): About 5 V 
E22 WHT/BLK BKSW 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 
E29 BRN SCS Detects service check signal With the SCS shorted with the HDS: About 0 V
With the SCS open: About 5 V