Theory Of Operation

This diagnostic checks if the leakage of the hydraulic circuit is below an acceptable amount. The purpose of this diagnostic is to protect the electro pump and to detect which hydraulic components are not working as expected. A small amount of leakage is normal due to the presence of electrovalves in the circuit. The Transmission Controller Module (TCM) uses leakage estimation models based upon fluid temperature, hydraulic pressure and electrovalves status. If the decrease in hydraulic pressure in a defined amount of time is greater than allowable, a leakage failure is detected. There are four leakage monitoring strategies used by this diagnostic: Circuit leakage with all electrovalves switched off. Odd clutch electrovalve leakage during regulation (switched on). Even clutch electrovalve leakage during regulation (switched on). Gate select electrovalve leakage during regulation (switched on).