Theory Of Operation

The odd clutch normally functions at positions in between fully engaged (clutch closed) and fully disengaged (clutch open). This diagnostic checks if the odd clutch is stuck in a position closer to the clutch open position than the requested position. This is caused either by a mechanical failure of the clutch or by a blocked odd clutch solenoid valve which keeps fluid pressure high and the clutch open. When the solenoid valve current is low, the valve is venting and the odd clutch is engaged. A failure is detected when the actual odd clutch position (read from sensor) is closer to the clutch open position than the requested position as compared to a calibratable threshold and the solenoid valve current (computed by the closed loop control) is significantly lower than the zero flow current.