Transmission Management

The transmission management system uses both analogue and digital signals, to control the operation of the transmission. Digital signals are processed by the TCM to and from the vehicle multiplex network. Other input/output analogue signals are hardwired to the TCM. This information is used primarily by the TCM to decide which shift program to implement, which gear to select and for shift energy management. If a fault occurs, the TCM will take default action and inform the driver via the Message Center and amber warning light.

Harness Connector
The vehicle harness connector for the TCM is an 88-way latching connector. The TCM is wired to the electrical pressure regulators/solenoids, oil temperature sensor and shaft speed sensors in the transmission casing.

Sport Mode
When sport mode is selected by the driver using the mode switch, the sport pattern is only activated when a set cornering force is achieved, or the kickdown switch is pressed. The vehicle speed and the difference in speeds between the two front wheels is used to calculate the amount of cornering force.

Torque Convertor Lock-up
The torque convertor lock-up clutch is engaged as a function of throttle position, output speed, oil temperature, gear shift and shift program. Lockup is possible in 2nd, 3rd, 4th and 5th gears but is usually restricted to 4th and 5th gears. During a gear shift the TCM controls the amount of slip of the lock-up clutch to enhance shift quality.

Oil Temperature
When the engine coolant or transmission oil temperature exceeds set thresholds a hot mode program is selected which locks the torque convertor clutch, minimizing the amount of heat entering the engine cooling system from the transmission oil.


Gear Shift Interlock
Gear shift interlock is controlled by the BPM, part of the SCP network. The gearshift release will only be activated when the ignition is in position II, transmission is in Park and the brake pedal is depressed. Once transmission is out of Park, the brake pedal has no effect on gearshifting and the interlock is disabled.

Reverse Inhibit
Selection of reverse with the vehicle moving forwards above walking pace is electrically inhibited, unless the vehicle is in the default "limp-home" mode.

Kickdown
A floor mounted switch/pedal position sensor signals the TCM to select the lowest gear to give maximum torque for acceleration.

Torque Control
The TCM synchronizes the operation of the transmission clutches and invokes shift energy management to control engine output torque during a gear shift.

Traction Mode
The traction program compliments the traction control system and is implemented whenever traction control intervenes to maximize wheel stability.

Cruise Mode
Cruise mode reduces unwanted hunting of the transmission gearshifting and is activated when cruise control is resumed and when the vehicle is cruising near the set speed.

Gradient Mode
The gradient program enhances vehicle performance, driveability and cooling when the vehicle is climbing a gradient.

Start Inhibit
The rotary switch also provides the start inhibit function to the ECM, which will not allow an engine start until the gear selector is in either Park or Neutral.

Fault Monitoring/Diagnostics
The TCM constantly monitors the transmission system for faults. In the event of a fault occurring, the transmission is protected by a limp home mode. This mode allows use of P, R, N, and 4. It also signals the ECM to switch on the CHECK ENG (MIL) lamp.
The TCM is able to diagnose faults in components which affect exhaust emissions. Communication with the PDU (Portable Diagnostic Unit) is through the J1962 connector which allows accurate diagnosis of transmission problems. Additional diagnostic functions facilitate fast repair of faults. All transmission OBDII information is stored for future data analysis in the ECM.

Can Messages
Messages on the CAN data bus used or output by the TCM are detailed below:

Note: This list does not include network monitoring or diagnostic related messages.

Message Used by TCM
TRACTION STATUS
ABS STATUS
FRONT LEFT WHEEL SPEED
FRONT RIGHT WHEEL SPEED
ESTIMATED ENGINE TORQUE
THROTTLE VALVE POSITION
ACCELERATOR PEDAL POSITION
TORQUE REDUCTION
ACKNOWLEDGE
ENGINE SPEED
CRUISE STATUS
BRAKE PEDAL DEPRESSED
ENGINE COOLANT TEMPERATURE
ENGINE MALFUNCTION

Source/ Used by
Brake Control Module
Instrument Cluster
ECM

Message Produced by TCM
TRANSMISSION INPUT SPEED
TRANSMISSION OUTPUT SPEED
TORQUE CONVERTER SLIP
KICKDOWN SWITCH
GEAR POSITION ACTUAL
TORQUE CONVERTER STATUS
TRANSMISSION SHIFT MAP
TRANSMISSION MALFUNCTION
TRANSMISSION FAULT CODES
GEAR POSITION ACTUAL
GEAR POSITION SELECTED
TRANSMISSION OIL TEMPERATURE
TRANSMISSION MALFUNCTION
TORQUE REDUCTION REQUEST
TRANSMISSION OVERLOAD
TRANSMISSION INPUT SPEED
TRANSMISSION OUTPUT SPEED
TORQUE CONVERTER SLIP
KICKDOWN SWITCH
GEAR POSITION ACTUAL
TORQUE CONVERTER STATUS
GEAR POSITION SELECTED
TRANSMISSION SHIFT MAP
TRANSMISSION OIL TEMPERATURE
TRANSMISSION MALFUNCTION
TRANSMISSION FAULT CODES