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: Operation: Notes
The Transmission Control Module controls all electronic operations of the transmission. The Transmission Control Module receives information regarding vehicle operation from both direct and indirect inputs and selects the operational mode of the transmission. Direct inputs are hard wired to and used specifically by the Transmission Control Module. Indirect inputs originate from other components/modules and are shared with the Transmission Control Module via the vehicle Controller Area Network (CAN) bus.
Some examples of direct inputs to the Transmission Control Module are:
- Battery (B+) Voltage
- Traction System Relay
- Trans Temp Sensor - P/N Switch
- N2 and N3 Speed Sensors
- Transmission Oil Temperature Sensor
Some examples of indirect inputs to the Transmission Control Module are:
- Controller Area Network (CAN) Bus Modules
- DRB III(R) Scan Tool Communication
- Shift Lever Assembly
- Brake Lamp Switch
Based on the information received from these various inputs, the Transmission Control Module determines the appropriate shift schedule and shift points, depending on the present operating conditions and driver demand. This is possible through the control of various direct and indirect outputs.
Some examples of Transmission Control Module direct outputs are:
- 1-2/4-5 Solenoid
- 2-3 Solenoid
- 3-4 Solenoid
- TCC Solenoid
- Modulation Pressure Solenoid
- Shift Pressure Solenoid
Some examples of Transmission Control Module indirect outputs are:
- Transmission Temperature (to Powertrain Control Module)
- Shift Lever Position (to Powertrain Control Module)
In addition to monitoring inputs and controlling outputs, the Transmission Control Module has other important responsibilities and functions:
- Storing and selecting appropriate Shift Schedules
- System self-diagnostics
- Diagnostic capabilities (with DRB III(R) scan tool)
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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.
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