Lock-Up Solenoid, SLU
The lock-up-solenoid, SLU is located in the gearbox control system, which is mounted on the front edge of the gearbox.
The lock-up-solenoid, SLU consists of an electric coil that controls a hydraulic valve. The solenoid is controlled, like all linear solenoids in the gearbox, by a pulsed (PWM) current with a frequency of 300Hz and grounded via the Transmission Control Module (TCM). The average value on the current signal that deploys the solenoid varies between 0.1 A and 1 A and the demand controls the deployment.
The solenoid controls the torque converter's Lock-up engagement. Engagement occurs by the solenoid pulsing, which gives a smooth engagement of the lock-up function. The solenoid allows the torque converter to work in one of three positions:
- Open
- Controlled slipping
- Locked.
The hydraulic function of the solenoid is linear.
There is a diagnostic for the lock-up solenoid.