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 (TCM)
The transmission control module (TCM) primarily controls shift points and lockup engagement.
The transaxle is controlled by an electronic shift system. The TCM processes input signals. From the information received, the TCM controls the transaxle hydraulic system.
The four inputs to the TCM from the internal park/neutral position switch assembly indicate which position is selected by the transmission selector lever. This information is used for engine controls as well as determining the transmission shift patterns. The state of each input is available for display on the scan tool. The four input parameters represented are Mode A, Mode B, Mode C and Mode PA (P/N Start). The TCM also communicates the park/neutral switch status to the BCM via serial data.
The electronic shift system consists of the following components:
- TCM
- Shift Solenoid (SS1 and SS2)
- Pressure Control Solenoid (PSC)
- Lockup Solenoid
- Input Shaft Speed (ISS) Sensor
- Output Shaft Speed (OSS) Sensor
- Transmission Fluid Temperature (TFT) Sensor
- Park/Neutral Position (PNP) Switch
NO RELATED
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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.