Transmission Electronic Control System

NOTE: The TCM is internal to the PCM on the 3.5L and 3.7L engines, and is an external module on the 3.2L diesel engine. To simplify this information it will be referred to as the PCM/TCM.

The PCM/ TCM control the electronic functions of this transmission. A plastic molded leadframe is bolted to the main control assembly. The leadframe contains the TSS, OSS, TFT and TR sensors.

The PCM/ TCM receives input signals from engine and transmission sensors and uses these inputs to control line pressure, shift time, TCC, and shift solenoids. The PCM/ TCM 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/ TCM along with module information from the vehicle CAN:

Engine speed
Engine torque
ECT
Engine Oil Temperature (EOT)
TP
APP
BPP
ABS wheel speed
Traction Control (ATC) status

The PCM/ TCM also:

Monitors inputs and outputs for the presence of faults.
Stores DTCs related to detected faults.
Provides outputs on the CAN for TR, OSS, TSS, TFT, current gear and A/C inhibit.
Provides OBD information using the CAN to illuminate the MIL or Transmission Control Indicator Lamp (TCIL).
Provides diagnostic information to a scan tool through the DLC.

If the PCM/ TCM detects a system or component fault, it substitutes a default value or signal using Failure Mode and Effect Management strategies.

The PCM/ TCM 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