System Overview: Signals

The table below summarizes the input signals to and output signals from the transmission control module (TCM). The signal types are divided into directly connected signals, serial communication and Controller area network (CAN) communication. The following illustration displays the same information with the Volvo component designations.

Input signals	Output signals
Directly connected:	Directly connected: (power supply unless otherwise stated)
Speed sensor, input shaft (7/61). Provides information about the transmission input speed. Use to calculate the shifting process and to run diagnostics for the hydraulic/mechanical functions in the transmission. Speed sensor, output shaft (7/62). Provides information about the transmission output speed. Use to calculate the vehicle speed and to run diagnostics for the hydraulic/mechanical functions in the transmission. Oil temperature sensor (7/74). Provides information about the transmission oil temperature. Gear-shift position sensor (3/71). Provides the transmission control module (TCM) with information about the selected gear position of the transmission. Enables starting only in position P and N. Four trailing contacts are grounded in a unique pattern for each gear.	Shift solenoids, S1-S5 (8/38-39, 8/72-74). The transmission control module (TCM) checks which gear is active by activating the solenoids in different patterns. Lock-up solenoid, SLU (8/40). Adjusts the line pressure to a lock-up pressure. Also used for certain shifts. Line pressure solenoid, SLS (8/41). Adjusts the line pressure to a shift pressure and is activated for certain gears. Line pressure solenoid, SLT (8/71). Adjusts the linear line pressure when shifting.
Via serial communication:	Via serial communication:
Gear selector module (GSM) (3/156). Provides data about the status of the winter (W) mode button and the control signal during geartronic shifting.	Gear selector module (GSM) (3/156). Controls the solenoid for the shift-lock function, 8/36. Activated by a signal from the central electronic module (CEM).
Via Controller Area Network (CAN):	Via Controller Area Network (CAN):
Electronic throttle module (ETM) (4/50) /Electronic throttle unit (6/120) via the engine control module (ECM) (4/46): Throttle opening, used to calculate gear changes. Sport mode and kick-down Accelerator pedal (AP) position, used to calculate gear-shift timing. Steering wheel module (SWM) (3/130), via the central electronic module (CEM) (4/56). Cruise control, used to calculate acceleration depending on the position of the Resume and Set buttons. Brake control module (BCM) / ABS control module (4/16). Provides information about the vehicle speed and also the difference in speed between the left and right-hand wheels. Prevents upshifting if the difference in speed is above 40 km/h to protect the differential in the transmission. Engine control module (ECM) (4/46): Stop lamp switch ON/OFF, used during torque converter lock-up Engine coolant temperature (ECT), used for diagnostics for the transmission temperature sensor and for catalytic converter start-up (Cat-start) Engine speed (RPM) >400 rpm = engine running. Used to start the transmission oil pressure and diagnostic functions Engine speed (RPM), used to check the slipping rate of the torque converter and the pressure build up, affecting the shifting comfort Kick-down. If the accelerator pedal (AP) is depressed and the throttle is wide open the engine control module (ECM) transmits a signal to the transmission control module (TCM) about kick-down Current engine torque, used to check the line pressure.	Brake control module (BCM) / ABS control module (4/16): Current gear, used to transmit a signal not to regulate when shifting Vehicle speed, used as back-up. Engine control module (ECM) (4/46): Transmission temperature, used to compensate increased load at low oil temperatures Selected gear, used by the engine so that the engine can compensate for different loads Lock-up, used by the engine so that the engine can compensate for different loads Next gear planned by the transmission control module (TCM), used by the engine so that the engine can compensate for different loads The request about reduced engine torque when shifting, the engine reduces the engine torque when shifting Torque limiting request, the engine limits the engine torque, depending on the current gear and if winter mode (W) is selected Current gear selector lever position. Used to show the lever position in the driver information module (DIM) Lights the malfunction indicator lamp (MIL) in the driver information module (DIM). Checking the malfunction indicator lamp (MIL), lamp lights in the event of emission related faults. Driver information module (DIM) (5/1): Current gear selector lever position. Used to show the lever position in the driver information module (DIM) Via the central electronic module (CEM), checking the warning lamps. The warning lamp lights orange in the event of a fault Via the central electronic module (CEM), text message in the driver information module (DIM). The driver can receive up to five error messages from the transmission control module (TCM). Rear electrical module (REM) (4/58). The transmission control module (TCM) transmits signals via the central electronic module (CEM) to light the back-up (reversing) lamp.

Fig 1: Identifying Transmission Control Module Input And Output Signals

Courtesy of VOLVO CARS CORPORATION