Perform this preliminary test before a hoist or road test in order to make sure that the electronic control inputs connections are tight and that the electronic control unit functions properly. If you do not check the inputs before operating the transmission, a simple electrical condition could result in misdiagnosis, usually as a major transmission condition.

Use a scan tool on the Hydra-Matic 4L30-E transmission for accurate diagnosis because the scan tool provides valuable information.

1. Move the gear selector to Park (P) and set the parking brake.
2. Connect the scan tool to the DLC.
3. Start the engine.
4. Verify that the following parameters are indicating live data:

•	The Engine Speed

•	The Output Speed

•	The Trans Range Switch

•	The Pressure Control Solenoid Current

•

The ECT

•	The Trans Fluid Temp

•	The Battery Voltage

5. Monitor the Brake Switch while tapping the brake pedal with your foot.

The scan tool display should indicate applied when you depress the pedal, and released when you release the brake pedal.

6. Monitor the Trans Range Switch and move the gear selector through all of the ranges.

•	Verify that the scan tool display matches the gear range that is indicated on the instrument panel or the console.

•	The gear selections should be immediate and not harsh.

7. Move gear selector to neutral and monitor TP Load Signal while increasing and decreasing engine RPM with the accelerator pedal.

TP Load Signal should increase with engine RPM.

8. With the transmission in Drive 4, press the Sport Mode Selector Switch several times while observing the Sport Mode Indicator Lamp on the I/P, and the Sport Mode Indicator Lamp and Sport Mode Selector Switch parameters on the scan tool. All should toggle between on and off.
9. With the transmission in Drive 4, press the Winter Mode Selector Switch several times while observing the Winter Mode Indicator Lamp on the I/P, and the Winter Mode Indicator Lamp and Winter Mode Selector Switch parameters on the scan tool. All should toggle between on and off.
10. Monitor A/C Request. Turn the A/C on and off. The scan tool parameter should toggle on and off.

If any of the previous tests resulted in improper operation, refer to the appropriate diagnostic procedure.