For 1990-2009 cars

The 4T45 automatic transmission uses a line pressure control system, which has the ability to continuously adapt the system line pressure. This compensates for normal wear of the following parts:

• | The clutch fiber plates

• | The seals

• | The springs

The transmission control module (TCM) maintains the Upshift Adapt parameters for the transmission. The TCM monitors the input speed sensor (ISS) and the output speed sensor (OSS) during commanded shifts in order to determine if a shift is occurring too fast or too slow. The TCM adjusts the signal from the transmission pressure control (PC) solenoid in order to maintain a set shift feel.

Transmission adapts must be set again when the transmission is overhauled or replaced. In order to set the transmission adapts again, select the following:

1. Scan Tool
2. Special Functions
3. Transmission Output Controls
4. Reset Transmission Adapts