Torque Converter Clutch Pulse Width Modulation (TCC PWM) Solenoid Valve (352)
The TCC PWM solenoid valve is a normally-closed, pulse width modulated (PWM) solenoid used to control the apply and release of the converter clutch. The TCM operates the solenoid with a negative duty cycle, at a fixed frequency of 32 Hz, to control the rate of TCC apply/release. The solenoid's ability to 'ramp' the TCC apply and release pressures results in a smoother TCC operation.
When vehicle operating conditions are appropriate to apply the TCC, the TCM increases the duty cycle to allow the TCC PWM solenoid valve to command TCC signal fluid pressure at a level sufficient to move the TCC enable valve and the TCC control valve to the apply position. Release pressure is directed to exhaust, and regulated apply 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 PWM 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 TCC enable valve and the TCC control valve to the release position. Apply fluid is directed to exhaust and converter feed fluid is directed into the release 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, or brake switch activation, depending on vehicle application.
TCC PWM solenoid valve resistance should measure between 10.0-11.5 Ω when measured at 20°C (68°F). The resistance should measure approximately 16 Ω at 150°C (300°F).