Input Speed Sensor (ISS)

Input Speed Sensor (ISS)

The input speed sensor provides transmission input shaft speed information. This signal is produced from an inductive pick-up, generating 36 pulses per revolution.

Output Speed Sensor (OSS)

The output speed sensor provides transmission output shaft speed information. This signal is produced from an inductive pick-up, generating 36 pulses per revolution.

Accelerator Pedal Position (APP) Sensor

The accelerator pedal position (APP) sensor is a potentiometer mounted on the accelerator pedal. The APP sensor detects the position of the accelerator pedal and sends this information to the TCM. The APP sensor is used for shift scheduling and TCC lock-up.

Engine Coolant Temperature (ECT) Sensor

The engine coolant temperature (ECT) sensor detects engine coolant temperature and supplies the information to the TCM. The ECT sensor is used to control the torque converter clutch (TCC) operation.

Transmission oil Temperature (TFT) Sensor

A thermistor provides an electrical indication of the oil temperature. The signal is measured as a voltage with reference to analogue ground in the TCM.

Virtual Kickdown Switch

Kickdown is intended to provide maximum vehicle acceleration, via the appropriate downshift(s), when the operator uses full throttle. The kickdown switch provides an electrical signal when the accelerator pedal is fully pressed down. The TCM detects kickdown using the accelerator pedal position.

Position sensor

The TCM uses the position of this switch, housed on the TCM and main control valve body, to determine the selected gear range. Gear selections are sent by CAN to the TCM, which operates the transmission selector shaft between positions Park, Reverse, Neutral and Drive. The TCM detects the driver´s choice of manual range selection.

Transmission Range Switch (TRS)

The transmission range switch detects the position of the transmission selector shaft. The switch is supplied as part of a new transmission assembly, mounted on the transmission body. The switch is used to indicate positions of the shaft: Park, Reverse, Neutral, Drive, Fourth, Third and Second.

TCM Monitoring Functions

The TCM monitors all input and outputs to identify possible failures. If a fault is detected the TCM takes the appropriate action to ensure the transmission enters a safe mode of operation, without sacrificing transmission durability or driver safety.

Supply Monitoring

If the battery voltage is either too great or too low, the TCM will detect a fault condition. For the TCM to be able to identify this fault, the engine must be running and the transmission oil temperature sensor must be functioning correctly.

Solenoid Supply Monitoring

While the solenoid operating transistors are being activated, checks are run for open circuits, shorts circuits to ground and short circuits to supply. The monitoring function evaluates the voltage characteristics during the switch on process checking for the above faults. All solenoid outputs are fully protected. The processor and the appropriate fail-safe action taken can quickly identify open and short circuit faults.

Sensor Supply Monitoring

The sensor supply voltage is a stabilized supply. This supply is monitored by the TCM by an Analogue to Digital Converter (ADC). If the voltage is out of the valid tolerance a diagnostic trouble code (DTC) is set and the appropriate fail-safe action is performed.

Electronically Erasable Programable Read Only Memory (EEPROM) Monitoring

To diagnose errors with the Electronically Erasable Programable Read Only Memory (EEPROM) the TCM calculates four checksums continuously: If the processor identifies discrepancies in any of the four checksums the TCM will engage ‘mechanical’ limp-home mode. Diagnosis is only performed during TCM initialization. There is no fail-safe mechanism associated with this function as the EEPROM is mainly used for the storage of fault codes and transmission calibration adoptions. If a fault occurs the TCM is able to perform default action and inform the driver of the problem, this is by the DIM message centre right.

Watchdog Monitoring

Watchdog monitoring has two functions. Firstly, it checks that it is possible to inhibit output control by the activation of the solenoid supply transistor. Secondly, it checks that the safety circuit is functioning correctly. During initialization the watchdog checks that it is possible to inhibit control of the pressure regulator and solenoid valves by switching the solenoid supply transistor. There is a fault if activation of the solenoids cannot be inhibited by the watchdog.

The supply to the solenoids can still be inhibited by the high side switch responsible for control of each solenoid i.e. One safety path is lost.