Programmable automatic transmission control unit (PCU)
The programmable transmission control unit (PCU) is an electronic device that controls the operation of an automatic transmission (AT). It receives signals from various sensors in the car, such as:
* Throttle Position Sensor
*Car speed sensor
* Automatic transmission temperature sensor
* Automatic transmission pressure sensor
PCU functions
The PCU uses these signals to determine:
* When to change gears
*What gear ratio to use
* How to control torque converter lockup
* How to control other automatic transmission functions
PCU programming
The PCU is usually programmed by the vehicle manufacturer, but can be reprogrammed to tailor it to the vehicle’s specific needs and driving style. Reprogramming can be performed using a diagnostic scanner and appropriate software.
Benefits of PCU reprogramming
Reprogramming the PCU can improve automatic transmission performance in the following aspects:
*Smoother gear shifting
* Increased fuel efficiency
* Improved performance
* Increased service life of automatic transmission
PCU types
There are several types of PCUs, including:
*Hydraulic PCUs: Use hydraulic valves to control the automatic transmission.
*Electrohydraulic PCUs: Combine hydraulic valves with electronic control.
* Electronic PCUs: Fully electronic and use solenoids to control the automatic transmission.
PCU location
The PCU is usually located inside or near the automatic transmission.
Differences from TCM
The PCU is sometimes called the transmission control module (TCM). Although they perform similar functions, they are not interchangeable. The PCU is part of the automatic transmission, and the TCM is usually a separate device.