Transmission control unit (TCU)
Location:
The TCU is usually located near or inside the transmission.
Functions:
The TCU is responsible for controlling the operation of the automatic transmission. It performs the following functions:
* Continuous monitoring of transmission parameters such as engine speed, vehicle speed, throttle position and transmission fluid temperature.
* Selection of optimal gear based on input data from sensors.
* Gear shift control by controlling the valve body solenoid valves.
* Adjust engine torque to ensure smooth gear shifting.
* Provides transmission protection by limiting engine torque when necessary.
Fault codes:
When the TCU detects a malfunction, it stores a trouble code (DTC) in memory. Common TCU trouble codes include:
* P0700: Transmission control system malfunction
* P0715: Turbine Speed Sensor (TSS)
* P0730: Wrong gear ratio
* P0740: Transmission hydraulic system
* P0750: Shift Solenoid
TCU replacement:
The TCU may need to be replaced if it is faulty or if the transmission has been overhauled. When replacing a TCU, it must be programmed to be compatible with the vehicle and transmission.
Notes:
* The TCU may also be called the transmission control module (TCM) or transmission control unit (GBU).
*TCU location and function may vary depending on vehicle make and model.