Subaru Impreza automatic transmission control unit
The automatic transmission control unit (ATM) is an electronic device that controls the operation of the transmission. It receives signals from sensors and switches and then uses this information to control valves and solenoids that change gears.
Location of the automatic transmission control unit
In a Subaru Impreza, the automatic transmission control unit is usually located under the hood, next to the battery. It can be mounted on the body or on a separate bracket.
Functions of the automatic transmission control unit
The automatic transmission control unit performs several important functions, including:
* Monitoring vehicle speed, engine load and transmission slip
* Determining the optimal gear shift moment
* Transmission hydraulic pressure control
* Torque converter lock-up adjustment
* Diagnostics and activation of the automatic transmission warning light (if applicable)
Main elements of the automatic transmission control unit
The automatic transmission control unit usually consists of the following elements:
* Microcontroller: This is the main computing device that controls the operation of the automatic transmission control unit.
* Memory: Stores automatic transmission control programs, gear shift tables and diagnostic trouble codes.
* Gauges and Switches: Provide information about vehicle speed, throttle position, transmission temperature and other parameters.
* Valves and solenoids: Control hydraulic pressure in the transmission and shift gears.
* Connectors: Provides electrical connections to sensors, switches, and wiring harness.
Troubleshooting the automatic transmission control unit
If problems arise with the operation of the automatic transmission, the control unit may be one of the possible faults. Common signs of a faulty automatic transmission control unit include:
*Hard shifting
* Sliding gears
* Lack of interaction
* Automatic transmission warning light comes on
To diagnose faults in the automatic transmission control unit, a diagnostic code scanner is required. The scanner can read fault codes stored in the control unit’s memory, which may indicate a specific fault.
If the automatic transmission control unit is faulty, it must be replaced. It is recommended that you have a qualified mechanic experienced in servicing Subaru transmissions perform the replacement and program the new control unit.