Powertrain Control Module (Pcm)

The PCM controls Torque Converter Clutch (TCC) operation, overdrive clutch operation and the governor pressure solenoid. The PCM determines shift points and TCC operation based on input signals received from transmission fluid temperature sensor, output shaft speed sensor, engine speed sensor, vehicle speed sensor and throttle position sensor.

There are 4 governor pressure curves programmed into the PCM. Governor pressure curves allow the PCM to adjust governor pressure for varying conditions. One governor pressure curve is used for operation when transmission fluid temperature is at or less than 30°F (1°C). The second governor pressure curve is used for operation when transmission fluid temperature is at or greater than 30°F (1°C) during normal city operation or highway driving. The third governor pressure curve is used for operation when wide open throttle (WOT) operation exists. The fourth governor pressure curve is used for operation when transfer case in low range.

The PCM controls TCC operation by operating the lock-up solenoid located on the valve body. Lock-up solenoid may be referred to as the TCC solenoid. If OD switch is in the ON position, the TCC will lock-up once transmission is in 4th gear with vehicle speed greater than 45 MPH. If OD switch is in the OFF position, the TCC will lock-up once transmission is in 3rd gear with vehicle speed greater than 35 MPH at light throttle application. When OD switch is in the OFF position, the OD light on the instrument panel will be illuminated.

The PCM prevents TCC operation and overdrive operation when transmission fluid temperature is less than 30°F (-1°C). If transmission fluid temperature exceeds 260°F (126°C), the PCM will cause a 4-3 downshift and engage the TCC. The OD light will be illuminated when the downshift occurs. Transmission will not upshift until transmission fluid temperature decreases to approximately 230°F (110°F).

The PCM contains a self-diagnostic system used for determining an electronic component failure. The PCM self-diagnostic system will store a Diagnostic Trouble Code (DTC) in the PCM memory if certain electronic problems exist.

DTC's can be retrieved using Chrysler's Diagnostic Readout Box (DRB) or generic scan tool. See SELF-DIAGNOSTIC SYSTEM . After repairing an electronic system problem, stored DTC must be cleared from PCM memory. For PCM location, see PCM LOCATION TABLE  table.