Theory Of Operation

This diagnostic checks the pressure level in the hydraulic circuit to ensure adequate pressure to manage gear shifting and clutch actuation. The Pressure Low failure is detected if the pressure falls below a minimum threshold. Two diagnostics are performed: Check if the pressure level is below a minimum value to perform a gear shift and check if the pressure level is below a minimum value to keep the clutch open. The two pressure thresholds that detect the malfunctions are not fixed parameters but are functions of fluid temperature. The failure is detected once the pressure falls below a minimum value to perform a gear shift. If the pressure falls below a minimum value to keep the clutch open, then more stringent recovery actions are taken.