Powertrain Control System
The PCM controls the electronic functions of this transmission. A plastic molded leadframe is bolted to the main control assembly. The leadframe contains the Turbine Shaft Speed (TSS), Output Shaft Speed (OSS), Transmission Fluid Temperature (TFT) and Transmission Range (TR) sensors.
The PCM receives input signals from engine and transmission sensors and uses these inputs to control line pressure, shift time, Torque Converter Clutch (TCC), and shift solenoids. The PCM also provides power and ground for the reverse lamp relay coil and provides a PARK/NEUTRAL start enable signal.
The following is a list of direct engine and driver inputs to the PCM along with module information from the vehicle Controller Area Network (CAN):
- Engine speed
- Engine torque
- Engine coolant temperature
- Throttle position
- Accelerator pedal
- Brake pedal
- ABS wheel speed
- Traction control status
The PCM also:
- monitors inputs and outputs for the presence of faults.
- stores DTCs related to detected faults.
- provides outputs on the CAN for transmission range, output shaft speed, turbine shaft speed, transmission fluid temperature, current gear and A/C inhibit.
- provides On-Board Diagnostic (OBD) information using the CAN to illuminate the Malfunction Indicator Lamp (MIL) or Transmission Control Indicator Lamp (TCIL).
- provides diagnostic information to a scan tool through the Data Link Connector (DLC).
If the PCM detects a system or component fault, it substitutes a default value or signal using Failure Mode and Effect Management strategies.
The PCM also uses Failure Mode and Effect Management strategies to compensate for electrical or mechanical shift solenoid and apply component faults that result in alternate shift patterns.
If the transmission loses complete electronic control, it operates in a fail-safe mode with:
- Maximum line pressure in all transmission ranges
- Functional PARK, REVERSE and NEUTRAL positions
- Operation in 3rd or 5th gear (depending on the failure conditions) when the selector lever is in the DRIVE, 3, 2 or 1 position
- TCC is released in all transmission ranges and gears