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.
Regulating The Lock-Up Function
Regulating the lock-up function takes place by means of the Transmission Control Module (TCM) activating the lock-up solenoid. The engagement takes place by means of the Transmission Control Module (TCM) controlling the lock-up solenoid linearly and adapting the hydraulic pressure. The basic parameters for engagement are the engine speed, accelerator pedal position and the rotation speed of the transmission input and output shafts. The pressurizing of the lock-up function can be adapted by means of reading off the changes in the rotation speed of the transmission input shaft during the gearshift processes and comparing them with the calculated values in the Transmission Control Module (TCM).
Two different lock-up functions are integrated: locked lock-up and slipping lock-up.
Locked lock-up
In normal conditions lock-up takes place at relatively low speeds in order to reduce fuel consumption.
The function locked lock-up only works when the transmission's temperature is above 20 °C.
Slipping lock-up
This function ensures smoother engagement with reduced vibration and decreased noise when a gear is engaged. In this mode, the torque converter clutch is engaged, but not fully locked.
The following conditions must be met in order for the function to activate:
- gear selector lever in D or MAN
- gear 2, 3, 4, 5 or 6
- transmission's input speed is between 1, 000 RPM and up to approx. 2, 000 RPM
- transmission oil temperature is 20 - 120 °C.
Due to the slipping of the torque converter, 50 RPM, the friction properties of the transmission oil are very important. The transmission oil's properties therefore differ from conventional ATF oil properties. Always use transmission oil specified for this transmission, otherwise the function of the transmission can be impaired.
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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.