Transmission Overview
In 1993, GM made some minor modifications to the 4L80E transmission; one of the biggest differences is a new transmission connector. The two shift solenoids still receive power whenever the key is on, and the computer still supplies ground to the solenoids to energize them.

The converter clutch solenoid receives a pulse width modulated signal, to provide smooth converter clutch operation.

Terminal Identification
Here’s a breakdown of the individual connector terminals:

Electronic Pressure Control
To check the electronic pressure control signal, connect your high-impedance voltmeter or signal monitor to the terminals shown. 

Checking the Shift Pattern
Here's how to connect your signal monitor to check the transaxle shift signals:

This is the shift pattern you should see with your signal monitor:

Forcing the Shift
Here’s the manual shift pattern you can expect with the transmission in failsafe:

Here’s how to force the 4L80E transmission to shift electrically:

First Gear
In first gear, only solenoid A receives ground.

Second Gear
To shift into second gear, the computer releases ground from solenoid A; neither solenoid is grounded.

Third Gear
To shift into third gear, the computer only grounds solenoid B.

Fourth Gear
To shift into fourth gear, the computer grounds both shift solenoids; the gray line is the connection necessary to apply the converter clutch.

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