Transmission Control Systems: Description and Operation
A: GENERAL
The electronic-hydraulic control system consists of various sensors and switches, a transmission control module (TCM) and the hydraulic controller including solenoid valves. The system controls the transmission proper including shift control, lock-up control, timing control, reverse inhibit control, engine control, line pressure control, auto pattern select control and shift timing control. It also controls the AWID transfer clutch. In other words, the system detects various operating conditions from various input signals and sends output signals to shift solenoids 1 and 2, low clutch timing solenoid, 2-4 brake timing solenoid, duty solenoids A, B, C and D (a total of eight solenoids).
B: INPUT SIGNAL
C: OUTPUT SIGNAL
D: CONTROL ITEM
E: THROTTLE POSITION SENSOR
The throttle position sensor provides electrical signals corresponding to the throttle position. The throttle position and accelerator depression speed are detected by this throttle position sensor output.
F: VEHICLE SPEED SENSOR 1 (REAR)
The vehicle speed sensor (output shaft rotation sensor) is mounted to the extension case (from the outside of the case). It detects the rear wheel speed based on the peripheral speed of the transfer clutch drum and sends sine wave signals (30 pulses per rotation) to TCM.
G: VEHICLE SPEED SENSOR 2 (FRONT)
The vehicle speed sensor (output shaft rotation sensor) is mounted to the transmission case (from the outside of the case). It detects the front wheel speed and sends sine wave signals (16 pulses per rotation) to TCM.
The TCM converts the signals into 4-pulse normal wave signals and outputs them to the engine control module (ECM) and the combination meter.
H: ATF TEMPERATURE SENSOR
This sensor is mounted to the control valve in the transmission. It detects temperature change as an analog electrical signal. The output characteristics of the sensor are shown below.
I: TORQUE CONVERTER TURBINE SPEED SENSOR
The torque converter turbine speed sensor (output shaft rotation sensor) is mounted to the transmission case (from the outside of the case).
The sensor reads the rotation speed of the periphery of the high clutch drum coupled to the input shaft, and sends sine wave signals (32 pulses per rotation) to the TCM. The TCM calculates the proportion of the input shaft speed to the vehicle speed and determines whether the shifting is to be made or not.
J: INHIBITOR SWITCH
The inhibitor switch assures safety when starting the engine. This switch is mounted on the right side of the transmission case, and is operated by the range selector lever.
When the selector lever is set to "P" or "N", the electrical circuit is connected in the inhibitor switch and the starter circuit is energized for cranking the engine.
When the selector lever is set to "R", "D", "3", "2", or " 1 " range, the electrical circuit is disconnected in the inhibitor switch. Hence engine cranking is disabled. In the "R" range, the backup light circuit is completed in the switch, and the backup lights come on.
In addition to the above function, the inhibitor switch incorporates a circuit for detecting the selected range position and sending the range signal to the TCM.
K: SHIFT SOLENOID 1 AND 2
These solenoids are mounted to the control valve. They are turned ON or OFF according to signals sent from the TCM. The gear positions are changed according to the ON and OFF condition of these solenoids.
L: LOW CLUTCH TIMING SOLENOID
This solenoid is mounted to the control valve, and it is turned ON or OFF according to the signal sent from the TCM. It then controls the low clutch timing valve B and reverse inhibit valve.
M:2-4 BRAKE TIMING SOLENOID
This solenoid is mounted to the control valve, and it is turned ON or OFF according to the signal sent from the TCM. It then controls the 2-4 brake timing valve B for decreasing the change gear shock.
N: DUTY SOLENOID A (LINE PRESSURE)
This solenoid is mounted to the control valve, and its duty ratio is controlled by the signal sent from TCM. This solenoid then controls the pressure modifier valve and accumulator control valve A to adjust the line pressure to an optimum pressure level suitable for operating conditions.
0: DUTY SOLENOID B (LOCK-UP)
This solenoid is mounted to the control valve, and its duty ratio is controlled by the signal sent from TCM. It then controls the lock-up control valve to provide smooth engagement and disengagement of the lock-up clutch.
P: DUTY SOLENOID D (2-4 BRAKE)
This solenoid is mounted to the control valve, and its duty ratio is controlled by the signal sent from TCM. It modulates the 2-4 brake duty pressure when the 2-4 brake is operated, reducing shifting shocks.
0: DUTY SOLENOID C (TRANSFER)
This solenoid is mounted to the transfer control valve on the rear end of transmission case, and its duty ratio is controlled by the signal sent from TCM. It then controls the transfer control valve for controlling the transfer clutch hydraulic oil pressure.