For 1990-2009 cars

The 4T65-E transmission uses a line pressure control system, which has the ability to continuously adapt the system's line pressure. This compensates for normal wear of the following parts:

• | The clutch fiber plates

• | The seals

• | The springs

This learning feature is similar to that which is used for fuel control and idle position.

The PCM maintains the following adapt parameter for the transmission:

Upshift Adapt -- The PCM monitors the Automatic Transmission Input (Shaft) Speed Sensor (A/T ISS) and the Vehicle Speed Sensor (VSS) during commanded shifts in order to determine if a shift is occurring too fast or too slow. The PCM adjusts the signal to the transmission Pressure Control Solenoid (PCS) valve in order to maintain a set shift feel.

Transmission adapts must be reset whenever the transmission is overhauled or replaced. In order to reset transmission adapts, select the following:

1. Scan tool
2. Miscellaneous test
3. A/T outputs
4. Clear or reset all adapts