TCC Lock Up Pressure Control Solenoid Valve (SLU) (339)
The TCC lock up pressure control solenoid valve is a normally low, 3-port linear pressure control solenoid used to control the apply and release of the 2nd (B2) and low and reverse (B3) clutches, and the torque converter clutch. The TCM operates the solenoid with a negative duty cycle at a fixed frequency of 32 Hz to control the rate of clutch apply/release. The solenoid's ability to "ramp" the clutch apply and release pressures results in a smoother clutch operation.
When vehicle operating conditions are appropriate to apply the TCC, the TCM increases the duty cycle to allow the TCC lock up pressure control solenoid valve to command lock up control (12) and TCC signal (13) fluid pressure at a level sufficient to move the lock up relay valve and the lock up control valve to the apply position. Release (4) fluid pressure is directed to exhaust, and apply (5) fluid is directed to the apply side of the converter pressure plate/damper assembly. The TCM then increases the duty cycle to control a slippage of 20-80 RPM between the pressure plate/damper assembly and the converter cover. This provides for improved filtration of engine vibrations and allows the TCC to apply at low engine speeds in 2nd, 3rd, 4th and 5th gear. At high speed, lock up mode is set by activating the TCC lock up pressure control solenoid valve at maximum duty cycle.
Release of the TCC is achieved by decreasing the duty cycle to a level low enough to allow spring force to move the lock up relay valve and the lock up control valve to the release position. Apply (5) fluid is directed to exhaust and converter feed (3) fluid is directed into the release (4) circuit to the release side of the pressure plate/damper assembly.
There are also some operating conditions that may prevent or enable TCC apply under various conditions (engine temperature, transmission temperature, brake switch activation) depending on vehicle application.
TCC lock up pressure control solenoid valve resistance should measure between 5.0 and 5.6 ohms when measured at 20°C (68°F).