Perform this preliminary test before a hoist test or a road test in order to make sure that the electronic control inputs are connected and operating. If you do not check the inputs before operating the transmission, you could misdiagnose a simple electrical condition as a major transmission condition.

A scan tool provides valuable information and must be used on the Hydra-Matic 4L60-E transmission for accurate diagnosis.

1. Move the gear selector to PARK, (P) and set the parking brake.
2. Connect the scan tool to the DLC terminal.
3. Start the engine.
4. Connect the power to the scan tool.
5. Verify that the following signals are present:

•	Engine speed

•	Transmission OSS

•	Vehicle Speed

•	TFP Sw. A/B/C

•	PRNDL Select

•	PC Sol. Ref. Current

•	PC Sol. Actual Current

•	PC Sol. Duty Cycle

•	TCC Brake Switch

•	4WD Low (4WD Only)

•

ECT

•	Trans. Fluid Temp.

•

TP Angle

•	Ignition Voltage

6. Monitor the BRAKE SWITCH signal while tapping the brake pedal with your foot. The BRAKE SWITCH should be on when the pedal is depressed. The brake switch should come off when the brake pedal is released.
7. Monitor the PRNDL SELECT signal and move the gear selector through all of the ranges.
8. Verify that the PRNDL SELECT value matches the gear range indicated on the instrument panel or console. Gear selections should be immediate and not harsh.
9. Move the gear selector to neutral and monitor the TP ANGLE signal while increasing and decreasing the engine RPM with the accelerator pedal. The TP ANGLE should increase with the engine RPM.