A/T System Description - Electronic Control System (KH)

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 receives input signals from the sensors, switches, and other control units, performs data processing, and output 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, all of which are 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 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 the 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 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 4th), 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.

 

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 Operation

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

Position Gear position Shift solenoid valves 
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 
2nd gear OFF ON OFF OFF 
1st gear ON ON ON OFF 
Shifting from the P and N position OFF ON OFF ON 
Stays in reverse ON ON OFF ON 
Reverse inhibitor control OFF OFF ON OFF 
Park OFF ON OFF ON 
Neutral OFF ON ON 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 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.

 

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 3rd to 4th gear, and from 2nd to 3rd gear (when the throttle is closed) becomes higher than the 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 in 4th gear, decelerating, and when you are applying the brakes on a steep hill, the transmission will downshift to a 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 engage and disengage 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 condition of lock-up starts.
The 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 2nd, 3rd, and 4th gears in the D position, and 3rd gear in the D position D3 driving mode.

 

PCM A/T Control System Electrical Connections

 

Electronic Control System (cont'd)


PCM A/T Control System 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 
A10 GRN/YEL SG2 Sensor ground Less than 1.0 V at all times 
A11 GRN/WHT SG1 Sensor ground Less than 1.0 V at all times 
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 Less than 1.0 V at all times 
A24 BRN/YEL LG1 Ground Less than 1.0 V at all times 

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 control With ignition switch ON (II): Pulsing signal 
B16 BRN/WHT LS B+ A/T clutch pressure control solenoid valve B control With ignition switch ON (II): Pulsing signal 
B24 BLU/YEL LS C+ A/T clutch pressure control solenoid valve C control With ignition switch ON (II): Pulsing signal 

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 control 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 Input shaft (mainshaft) speed sensor signal input With ignition switch ON (II): 0 V or about 5 V
With engine at idle in the N and P positions: 1.5-3.5 V (pulsing signal) 

Electronic Control System (cont'd)


PCM A/T Control System Inputs and Outputs (cont'd)


 

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 control With ignition switch ON (II): 0 V 
C10 BLU/WHT OP3SW 3rd clutch transmission fluid 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 the 2 position: 0 V
In other than the 2 position: About 5 V 
C12 RED/WHT ATP RVS Transmission range switch RVS (R position) signal input In the R position: 0 V
In other than the R position: About 5 V 
C13 BLU/RED OP2SW 2nd clutch transmission fluid 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 ATFT ATF temperature sensor signal input With ignition switch ON (II): 0.2-4.8 V
With ignition switch OFF: 0 V 
C15 BLU NC Output shaft (countershaft) speed sensor signal input With ignition switch ON (II): 0 V or about 5 V
When driving: About 1.5-3.5 V (pulsing signal) 
C16 WHT/BLU LS C- A/T clutch pressure control solenoid valve C control With ignition switch ON (II): 0 V 
C19 BRN ATP 1 Transmission range switch 1 position signal input In the 1 position: 0 V
In other than the 1 position: About 5 V 

PCM CONNECTOR D (17P)
Terminal Number Wire Color Signal Description Measuring Condition/Terminal Voltage 
D2 GRN D3 SW D3 switch signal input With ignition switch ON (II): About 5 V
With ignition switch ON (II) and D3 switch ON: 0 V 
D4 BLK/RED ATP N Transmission range switch N position signal input In the N position: 0 V
In other than the N position: About 5 V 
D5 WHT ATP R Transmission range switch R position signal input In the R position: 0 V
In other than the R position: About 5 V 
D6 BLU/BLK ATP P Transmission range switch P position signal input In the P position: 0 V
In other than the P position: About 5 V 
D10 WHT/GRN ATP D Transmission range switch D position signal input In the D position: 0 V
In other than the D position: About 5 V 

PCM CONNECTOR E (20P)
Terminal Number Wire Color Signal Description Measuring Conditions/Terminal 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), in the P position 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 on the DLC short-circuited to ground with HDS in SCS mode: 0 V