RAM 1500 Truck 2WD V8-5.7L VIN 2 (2006)
PRESSURE SWITCH STATES
A Diagnostic Trouble Code (DTC) will set if the TCM senses any switch open or closed at the wrong time in a given gear.
The TCM also tests the 2/4 and OD pressure switches when they are normally off (OD and 2/4 are tested in 1st gear, OD in 2nd gear, and 2/4 in 3rd
gear). The test simply verifies that they are operational, by looking for a closed state when the corresponding element is applied. Immediately after a
shift into 1st, 2nd, or 3rd gear with the engine speed above 1000 rpm, the TCM momentarily turns on element pressure to the 2/4 and/or OD clutch
circuits to identify that the appropriate switch has closed. If it doesn't close, it is tested again. If the switch fails to close the second time, the
appropriate Diagnostic Trouble Code (DTC) will set.
Sensor Variable Line Pressure
SENSOR VARIABLE LINE PRESSURE
DESCRIPTION
The line pressure sensor (2) is mounted on the top of the valve body, next to the pressure control solenoid 0).
The TCM utilizes a closed-loop system to control transmission line pressure. The system contains a variable force style solenoid, the Pressure Control
Solenoid. The solenoid is duty cycle controlled by the TCM to vent the unnecessary line pressure supplied by the oil pump back to the sump. The
system also contains a variable pressure style sensor, the Line Pressure Sensor, which is a direct input to the TCM. The line pressure solenoid
monitors the transmission line pressure and completes the feedback loop to the TCM. The TCM uses this information to adjust its control of the
pressure control solenoid to achieve the desired line pressure.
OPERATION
The TCM calculates the desired line pressure based upon inputs from the transmission and engine. The TCM calculates the torque input to the
transmission and uses that information as the primary input to the calculation. The line pressure is set to a predetermined value during shifts and when
the transmission is in the PARK and NEUTRAL positions. This is done to ensure consistent shift quality. During all other operation, the actual line
pressure is compared to the desired line pressure and adjustments are made to the pressure control solenoid duty cycle.
