Transmission Control Module (TCM)

The TCM is mounted in the passenger compartment and connects directly to the wiring harness. Two connectors are used to make connections between the vehicle wiring, the transmission, and the TCM. The TCM is an electronic control module that receives input and provides output to control the operation of the 4T45-E automatic transmission.

The TCM receives the following inputs from the engine control module (ECM):

• Engine speed and torque values
• Engine intake air temperature (IAT), and throttle position (TP) information
• Engine coolant temperature (ECT)
• Air-conditioning (A/C) status
• Cruise control status

The ECM provides this data to the TCM through the Keyword Serial Data. A two-wire circuit is used to communicate data between the ECM and TCM. Other TCM inputs are the following:

• Battery and ignition voltage
• Brake switch status
• Transmission fluid temperature (TFT)
• Transmission input speed sensor (ISS)
• Transmission output speed sensor (OSS)

The TCM provides the following outputs in order to control the automatic transmission:

• Line pressure control solenoid (PCS) valve regulates the transmission line pressure
• The torque converter clutch (TCC) enable solenoid valve is used to hydraulically select whether the TCC pressure control solenoid valve will control the fluid pressure used to apply the forward and reverse clutches or the fluid pressure used to apply the torque converter clutch
• TCC pressure control solenoid valve is used to control the fluid pressure used to apply and release the forward and reverse clutches, and the torque converter clutch

Other TCM outputs provided to the ECM are the following:

• MIL illumination request
• Vehicle speed
• Transmission input speed
• Transmission fluid temperature
• TCC status
• Torque reduction requests
• Park/Neutral Position Assembly status
• Transmission service status