General Description
The TCM controls the locking and unlocking of the Torque Converter Clutch ( or Damper Clutch ), to the input shaft of the transmission, by appling hydraulic pressure. The main purpose of T/C clutch control is to save fuel by decreasing the hydraulic load inside the T/C. The TCM outputs duty pulses to control the Damper Clutch Control Solenoid Valve( DCCSV ) and hydraulic pressure is applied to the DC according to the DCC duty ratio value. When the duty ratio is high, high pressure is applied and the Damper Clutch is locked. The normal operating range of the Damper Clutch Control duty ratio value is from 30%(unlocked) to 85%(locked).
DTC Description
The TCM increases the duty ratio to engage the Damper Clutch by monitoring the slip rpms (difference vlaue beteween engine speed and turbine speed ). If a very small amount of slip rpm is maintained though the TCM applies 0% duty ratio value, then the TCM determines that the Torque Converter Clutch is stuck ON and sets this code.
DTC Detecting Condition
Item | Detecting Condition | Possible Cause |
DTC Strategy | ? Stuck "ON" | ? TORQUE CONVERTER(DAMPER) CLUTCH : TCC ? Faulty TCC or oil pressure system ? Faulty TCC solenoid valve ? Faulty bady control valve ? Faulty TCM(PCM) |
Enable Conditions | ? Throttle position >20% ? Output speed >500rpm ? Manifold air pressure > 60kPa ? A/T range switch D,SP ? Time after TCC release >5secs |
Threshold Value | ? |Engine rpm - Input speed sensor rpm| = 20 rpm |
Diagnostic Time | ? More than 1sec |
Fail Safe | ? Damper clutch abnormal system (If diagnosis code P0742 is output four times, TORQUE CONVERTER(DEMPER) CLUTCH is not controlled by PCM/TCM) |