Electrical/Garage Shift Test

Perform this test before a road test in order to make sure that 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. Use the scan tool on the Hydra-Matic 4L80-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 power to the scan tool
5. Verify that the following signals are present on the scan tool:
- Transmission Input (Shaft) Speed Sensor (A/T ISS)
- Transmission Output(Shaft) Speed Sensor (A/T OSS)
- Automatic Transmission Fluid Pressure Manual Valve (TFP Val.) Position Switch
- Vehicle speed (MILES/HOUR)
- Current Gear
- Reference Transmission Pressure Control
- Solenoid Amperage (REF CURRENT)
- Actual Transmission Pressure Control Solenoid Amperage (ACT CURRENT)
- Engine Coolant Temperature (ECT)
- Automatic Transmission Fluid Temperature (TFT) Sensor
- TP Angle
- TCC Duty Cycle (TCC DC)
- System Voltage
- TCC Brake Switch
6. Monitor the TCC BRAKE signal while tapping the brake pedal with your foot. The brake switch signal should be:
OFF - when the brake pedal is released
ON - when the brake pedal is depressed
7. Monitor the Automatic Transmission Fluid Pressure Manual Valve Position Switch (TFP Switch) signal by moving the gear selector through all of the ranges. Verify that the TFP Switch state matches the gear range which is indicated on the instrument panel or on the console. Gear selections should be immediate and not harsh.
8. Move the gear selector to Neutral and monitor the Throttle Angle while increasing and decreasing engine RPM with the accelerator pedal. The Throttle Angle should increase with the engine RPM.