Theory Of Operation

WARNING: This page is about a different car, the 2013 RAM 3500 HD and 2013 RAM 2500 HD. However, it is still accessible from the selected car via links, so may be relevant.

Line pressure is measured by the Line Pressure Sensor (LPS) and regulation is achieved by changing the duty cycle of the Pressure Control Solenoid (PCS) controlled by the Transmission Control System, (5% duty cycle = solenoid off = Max line pressure, 62% duty cycle = solenoid on = Min line pressure). The Transmission Control System calculates the desired line pressure based on engine and transmission inputs.

The Transmission Control System calculates torque input to the transmission and uses this as the primary input for the desired line pressure calculation. This is called Torque Based Line Pressure. In addition, the line pressure is set to a preset level of 827 or 931 kPa (120 or 135 psi) during shifts and in Park or Neutral to ensure consistent shift quality. The actual line pressure is continuously being compared to the desired target line pressure. If the actual line pressure is consistently higher than the highest desired line pressure used in the current gear, the line pressure high DTC P0869 will set.