Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Transmission Control Module: Description
The transmission control module (TCM) receives, processes and sends various digital and analog signals related to the automatic transmission. In addition, it processes information received from other vehicle systems, such as engine torque and speed, accelerator pedal position, wheel speed, kick-down switch, traction control information, etc.
The TCM is located under the driver's seat and is connected to other control modules via a CAN bus. It controls all shift functions to achieve smooth shift comfort in all driving situations considering:
- Vehicle speed.
- Transmission status.
- Position of selector lever.
- Selected shift range.
- CAN signals.
- Engine Status.
Engine speed limits may be reached in all gears with full throttle or in kick-down operation. In forward driving, the shift range of the forward gears can be adjusted by the operator by tipping the selector lever to the left or right (AutoStick). However, the TCM features a downshift inhibitor to prevent the engine from overspeeding.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.