For a complete wiring diagram Refer to Section 8W

Theory of Operation

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 inputs from both the engine and transmission.

The Transmission Control System calculates torque input to the transmission and uses it as the primary input to the desired line pressure calculation. This is called Torque Based Line Pressure. In addition, the line pressure is set to a preset level 827 or 931kPa (120 or 135 psi) during shifts and in Park and 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 lower than the target while driving, the line pressure low DTC P0868 will set.

• When Monitored:

  Continuously while driving in a forward gear.

• Set Condition:

  The PCM continuously monitors Actual Line Pressure and compares it to Desired Line Pressure. If the Actual Line Pressure is more than 15 psi below Desired Line Pressure for 3.5 seconds continuously will cause this DTC to set.

Diagnostic Test

• Refer to the Transmission category and perform the appropriate symptom.

NOTE: This counter only applies to the last DTC set.

CAUTION: Removal of the Ignition Switch Feed fuse from the TIPM will prevent the vehicle from being started in gear.

WARNING: The Ignition Switch Feed fuse must be removed from the TIPM. Failure to do so can result in personal injury or death.

NOTE: All three scan tool Line Pressure readings should be steady and +/- 14 kPa (2.0 psi) of the reading specified on the Transmission Simulator.

NOTE: Make sure the Primary Transmission Oil Filter and/or O-ring is not cracked or split.

CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller tool #8815 to perform diagnosis.