Transmission Overview
The 4L30E is an electronically-controlled version of the 180C transmission, with an overdrive section added. The two shift solenoids are grounded all the time; the computer supplies power to the solenoids to energize them. Mainline pressure is controlled by the computer through a pulsed EPC solenoid.

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

Shown from the terminal side of the transmission connectors.

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:

Backprobe the terminals with the harness
connector still connected to the transmission.

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

The far right LED indicates the signal to the converter clutch (TCC) solenoid.

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

And here's how to force the 4L30E to shift electrically:

First Gear
In first gear, only the 2-3 solenoid receives power.

Second Gear
To shift into second gear, the computer adds power to the 1-2/3-4 solenoid.

Third Gear
To shift into third gear, the computer removes power from the 2-3 solenoid.

Fourth Gear
To shift into fourth gear, the computer removes power from the 1-2/3-4 solenoid—neither solenoid receives power.

Lockup
To apply the converter clutch, the computer provides power to the TCC solenoid.

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