System Overview: Signals

The table below summarizes the input signals to and output signals from the gearbox 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 gearbox input speed. Used to calculate the shifting process and to run diagnostics for the hydraulic/mechanical functions in the gearbox. Speed sensor, output shaft (7/62). Provides information about the gearbox output speed. Used to calculate the vehicle speed and to run diagnostics for the hydraulic/mechanical functions in the gearbox. Temperature sensor (7/74). Provides information about the gearbox oil temperature. Gear-shift position sensor (3/71). Provides the gearbox control module (TCM) with information about the selected gear position of the gearbox. Enables starting only in position P and N. Four trailing contacts are grounded in a unique pattern for each gear. Pressure sensor Lock-up . Provides the gearbox control module (TCM) with information about the gearbox oil pressure and selected gear.	Shift solenoids, S1-S2 . The gearbox control module (TCM) checks which gear is active by activating the solenoids in different patterns. Lock-up solenoid, SL . Activates the Lock-up function. Line pressure solenoid, STH . Adjusts the line pressure of the gearbox when shifting.
Via serial communication:	Via serial communication:
Gear selector module (GSM) (3/156). Provides information about the gear selector position: If the selector is in position D or in the Geartronic mode, or if up or down shifting occurs in the Geartronic position.	Gear selector module (GSM) (3/156). Controls the solenoid for the shift-lock function (8/36). Activated on request by the central electronic module (CEM) (4/56).
Via Controller Area Network (CAN) communication:	Via Controller Area Network (CAN) communication:
Engine control module (ECM) (4/46). Accelerator pedal (AP) position, used to calculate the 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) / Anti-lock brake system module (ABS) (4/16). The difference in speed between the right and left-hand wheels. Requests a reduction in torque if the differential speed is too high. Engine control module (ECM) (4/46): Brake lamp switch ON/OFF, used during the torque converter lock-up function Engine coolant temperature (ECT), used to diagnose the gearbox temperature sensor 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 gearbox control module (TCM) about kick-down Current engine torque, used to check the line pressure.	Brake control module (BCM) / Anti-lock brake system module (ABS) (4/16): Current gear, used to transmit a signal so there is no STC (Stability and traction control) when shifting Vehicle speed, used as reverse. Engine control module (ECM) (4/46): Gearbox temperature, used to compensate increased load at low oil temperatures Selected gear, used by the engine so that it can compensate for different loads Lock-up, used by the engine so that it can compensate for different loads Next gear ordered by the gearbox control module (TCM), used by the engine so that it can compensate for different loads Torque reduction during shifting. This is achieved by retarding the ignition Torque limiting request, the engine limits the engine torque depending on the current gear. This is achieved by controlling the throttle opening Lights the malfunction indicator lamp (MIL) in the driver information module (DIM). Checking the malfunction indicator lamp (MIL), lights the lamp 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. Lights the orange/yellow warning lamp 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 gearbox control module (TCM). Rear electrical module (REM) (4/58). The gearbox control module (TCM) transmits a signal via the central electronic module (CEM) to light the reversing lamp.

Fig 1: Transmission Control Module (TCM) Input/Output Signals

Courtesy of VOLVO CARS CORPORATION