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.
System overview: Components
The following components are included in the control system for the automatic transmission (4T65EV):
- The transmission control module (TCM) - Controls the solenoids
- Shift solenoid, S1 - Controls shifting in the transmission
- Shift solenoid, S2 - Controls shifting in the transmission
- Lock-up solenoid, SL - Controls the torque converter lock-up function
- Line pressure solenoid, STH - Controls the transmission line pressure
- Transmission input speed sensor (input shaft speed) (5) - Provides the transmission control module (TCM) with information about the input shaft speed. This is measured on the turbine side of the torque converter
- Speed sensor (output shaft speed) (7) - Provides the transmission control module (TCM) with information about the output shaft speed from the transmission
- Temperature sensor (6) - Provides the transmission control module (TCM) with information about the oil temperature of the transmission
- Gear-shift position sensor (8) - Provides the transmission control module (TCM) with information about the selected gear position (PRND321)
- Pressure sensor lock-up (9) - Provides the transmission control module (TCM) with information about the transmission oil pressure and selected gear
- Gear selector module (GSM) - Provides the transmission control module (TCM) with information about the gear selector position: If the selector is in position D or in the Geartronic mode, or if up or down shifting occurs in the Geartronic position.
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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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