Design

Design

Control module




The transmission control module (TCM) is positioned in an air cooled plastic box in the engine compartment together with the engine control module (ECM).

Shift solenoid S1 and S2




The shift solenoids S1 and S2 are positioned in the valve housing, which is mounted behind the side cover of the transmission. The shift solenoids (on/off type), consist of an electrical coil which controls a hydraulic valve. The solenoids are supplied with 12 V via the transmission control module (TCM) and grounded at the ground terminal. The shift solenoids control shifting and the transmission control module (TCM) determines which gear is to be used by activating them in different patterns.
There is a diagnostic for the electrical function of the shift solenoids. There is also a diagnostic for the hydraulic circuit, but not for the hydraulic function of the solenoids.

Lock-up solenoid, SL




Lock-up solenoid SL is positioned in the valve housing, which is mounted behind the side cover on the transmission. The lock-up solenoid consists of an electrical coil which controls a hydraulic valve. The solenoid is controlled by pulse width modulation (PWM) voltage and is grounded at the ground terminal. The solenoid controls lock-up engagement of the torque converter. Engagement occurs through solenoid pulsing which provides a smooth lock-up engagement function. Power transmission then changes to mechanical power transmission through the torque converter. The hydraulic function of the solenoid is linear.
There is a diagnostic for the electrical function of the solenoid, but not for the hydraulic function.

Pressure sensor Lock-up




The lock-up pressure sensor is positioned in the valve housing, which is mounted behind the side cover for the transmission. The lock-up pressure sensor consists of six electrical pressure switches. The pressure switches indicate the hydraulic pressure in the different transmission systems. The pressure sensor provides the transmission control module (TCM) with information about the system pressure and selected gear. The transmission control module (TCM) uses this information to control the lock-up solenoid, SL.
There are diagnostics for the lock-up pressure sensor.

Line pressure solenoid, STH




The line pressure solenoid, STH, is positioned in the valve housing, which is behind the side cover for the transmission. The line pressure solenoid consists of an electrical coil which controls a hydraulic valve. The solenoid is controlled by pulse width modulation (PWM) voltage and is grounded via the transmission control module (TCM). The function of the solenoid is linear. The hydraulic valve is controlled by the varied current which is the result of the pulse conditions. During high pulse conditions, (at high current (approximately 1A)) the line pressure is low. During low pulse conditions (at low currents) the line pressure is high. In the event of an open-circuit, the line pressure reaches maximum which will result in harsh gear shifting. This can also result in a whining noise from the transmission pump. The hydraulic valve is then completely open.
There are diagnostics for the solenoid. There is a diagnostic for the electrical function of the solenoid. There is also a diagnostic for the hydraulic circuit, but not for the hydraulic function of the solenoid. The hydraulic tests can be carried out using a mechanical pressure gauge. The idle and stop pressure can be checked.

Transmission input speed sensor (speed of the input shaft)




The transmission input speed sensor, (input shaft speed ) is positioned in the transmission housing. The sensor is an active sensor and is supplied with 12 V. When the driven gearwheel rotates, the sensor generates a pulsed current (quadratic wave) where the strength of the current depends on the position of the pulse wheel. The signals from the coil in the sensor are then effected by a magnetic resistance element, which generates a current which oscillates between 7 mA and 14 mA, and the frequency of which increase with speed. The transmission control module (TCM) calculates the transmission input speed using the signal from the sensor.
The input speed is compared with the transmission output speed from the transmission speed sensor signal to calculate the gear ratio.
There are diagnostics for the transmission input speed sensor.

Transmission output speed sensor (speed of the output shaft)




The transmission output shaft speed sensor is positioned on the transmission housing. The sensor is electro-magnetic and acts on a toothed pulse wheel. The sensor provides signals to the transmission control module (TCM) about the vehicle speed. The transmission speed sensor is an active sensor and is supplied with 12 V. When the pulse wheel rotates, the sensor generates a pulsed current (quadratic wave) where the strength of the current depends on the position of the pulse wheel. The signals from the coil in the sensor are then effected by a magnetic resistance element, which generates a current which oscillates between 7 mA and 14 mA, and the frequency of which increase with speed. The control module calculates the transmission output speed using the signals from the sensor. The signal is compared with the signal from the transmission input speed sensor and is used to calculate the gear ratio as well as for diagnostics.
There are diagnostics for the transmission output speed sensor.

Temperature sensor




The temperature sensor is the NTC resistive type. The temperature sensor is positioned on the valve housing inside the side cover and measures the transmission fluid temperature in the oil pan. The temperature sensor is supplied with 5 V and is grounded via the transmission control module (TCM). The control module can determine the transmission fluid temperature by measuring the voltage drop across the NTC resistor of the sensor. The control module stores the time the temperature has been within a certain temperature range. If a certain temperature and time has been exceeded, a diagnostic trouble code (DTC) indicating that a oil change is necessary is stored.
There are diagnostics for the temperature sensor.

Gear-shift position sensor




The gear-shift position sensor is located inside the transmission housing. It contains a Park / Neutral position (PNP) switch and switches which inform the transmission control module (TCM) about which gear is selected and whether back-up (reverse) gear is selected so that the reversing lamps are lit. The gear-shift position sensor is a position switch which is grounded via the chassis. The combination of pins A, B, C and PA indicate the current gear selector position (see the table below). The trailing contacts can either be closed or open. The gear-shift position sensor is not available as a replacement part.
There are diagnostics for the gear-shift position sensor.





Table for the gear-shift position sensor
The value indicates the position of the gear-shift position sensor (A, B, C and PA), see the table.
• = High signal (open)
- = Low signal (grounded)

Gear selector module (GSM)




The gear selector assembly is positioned in the center console and is mechanically connected to the transmission by a cable which moves the gear valve in the valve housing. The gear selector module (GSM) is positioned on the top panel of the gear selector assembly.
The gear selector module (GSM) receives gear position signals from the transmission control module (TCM) via serial communication. The transmission control module (TCM) receives the present gear position from the gear-shift position sensor. The LEDs in the top panel indicate the selected gear to the driver. The gear selector module (GSM) communicates serially with the central electronic module (CEM). The central electronic module (CEM) sends a signal to the gear selector module (GSM) to activate the shift-lock. The power supply and ground for the shift-lock solenoid are directly connected to the gear selector module (GSM).
The "W" switch in the gear selector assembly top panel is positioned on the printed circuit board for the gear selector module (GSM) and activates Winter mode. The gear selector module (GSM) checks the back-up (reverse) inhibitor function based on the vehicle speed signal from the transmission control module (TCM).
There are diagnostics for the gear selector module (GSM). Diagnostic trouble codes (DTCs) are stored in the transmission control module (TCM) in the event of a fault.

Gear selector assembly
There are two types of gear selector assembly for the 4T65EV (-GT). There is one gear selector assembly with seven positions and one with the Geartronic function.

Gear shift selector, seven positions




The gear selector has seven positions with the following functions:
- PPark position
- RBack-up (reverse) position
- NNeutral position
- DAutomatic shifting between all gears. (Does not apply when winter (W) mode is selected)
- 3Fourth gear is blocked in this position
- 2Only first and second gear function in this position
- 12nd, 3rd and 4th gears are blocked in this position.

Geartronic gear shift selector




Gear selector assemblies with Geartronic are unique in appearance and function. In addition to P/R/N/D modes they also have a "manual" (MAN) shifting mode.
The gear selector for Geartronic has the following functions:
- PPark position
- RBack-up (reverse) position
- NNeutral position
- DAutomatic shifting between all gears. (Does not apply when the mode selector is in winter mode (W), for further information see, Function/Shifting program (Winter mode))
- MANManual shifting. There are three hall sensors on the gear selector module (GSM). A permanent magnet on the gear selector lever affects the output signals of the sensors to the gear selector module (GSM).