Conduct the test according to the following steps:

1. Start the engine.
2. Depress the brake pedal.
3. Move the gear selector between the following positions:

Important: Transmission shifts should be immediate and not harsh.

•	Park to Reverse

•	Reverse to Neutral

•	Neutral to D4

Use the scan tool in order to see if any transmission malfunction codes have been set. If so, refer to Functional Test . After repairing the vehicle, perform the road test and verify that no codes have been set again.

If no codes have been set and the condition remains, refer to the Diagnostic Tables.

If the transmission is not performing well and no trouble codes have been set, check for an intermittent condition. Check all electrical connections for damage or a loose fit. Some scan tools have a snapshot test which can help to catch an intermittent condition that does not occur long enough in order to set a code.

If the condition is suspected to originate in the torque converter, refer to Torque Converter Clutch Diagnosis .

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 with the scan tool while tapping the brake pedal with your foot. The brake switch signal should be:

VCM

•	CLOSED - when the brake pedal is released

•	OPEN - when the brake pedal is depressed

PCM

•	OPEN - when the brake pedal is released

•	CLOSED - 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 Position Angle while increasing and decreasing engine RPM with the accelerator pedal. The Throttle Position Angle should increase with the engine RPM.

The vehicle computer calculates the upshift points based primarily upon two inputs:

When the VCM/PCM indicates that a shift should occur, an electrical signal is sent to the shift solenoids, which in turn move the valves to perform the upshift.

The shift speed charts refer to THROTTLE POSITION ANGLE instead of MIN THROTTLE or WOT in order to make shift speed measurement more uniform and accurate. Monitor THROTTLE POSITION ANGLE by using the scan tool.

Some scan tools have been programmed in order to measure and record shift point information. Check the instruction manual in order to see if this test is available.

With gear selector in D4, perform the following steps:

1. Refer to Shift Speed and choose a throttle position of either 15% or 20%.
2. Monitor the throttle position with the scan tool.
3. Accelerate to the chosen throttle position. Hold the throttle steady.

Important: Shift speeds may vary due to slight hydraulic delays in responding to electronic controls. A change from the original equipment tire size also affects shift speeds.

4. As the transmission upshifts, note the shift speed for each of the following gears:

•

2nd gear

•

3rd gear

•

4th gear

5. The Torque Converter Clutch (TCC) should apply in Third or Fourth gear. The TCC will not apply unless the engine coolant has reached a minimum operating temperature of approximately 54°C (130°F). Note when the TCC applies. If you do not notice the apply by an RPM drop, refer to Torque Converter Clutch Diagnosis .
6. Repeat steps 1-5 using several different throttle angles.

At vehicle speeds of 64-88 km/h (40-55 mph) in Fourth gear, quickly increase the throttle angle. Verify the following results:

At vehicle speeds of 64-88 km/h (40-55 mph) in Fourth gear, quickly increase the throttle angle to its maximum position. Verify the following results:

The shift solenoid valves do not control the initial downshift during manual downshifts. All manual downshifts are hydraulic. The solenoid states will change during, or shortly after, a manual downshift is selected.

1. At vehicle speeds of 64-88 km/h (40-55 mph) in Fourth gear, release the accelerator pedal while moving the gear selector to D3. Observe the following results:

•	The TCC releases

•	The transmission downshifts to Third gear immediately

•	The engine slows the vehicle down

2. Move the gear selector back to D4 and accelerate to 64-72 km/h (40-45 mph). Release the accelerator while moving the gear selector to D2 and observe the following results:

•	The TCC releases

•	The transmission immediately downshifts to Second gear

•	The engine slows the vehicle down

3. Move the gear selector back to D4 and accelerate to 48 km/h (30 mph). Release the accelerator pedal while moving the gear selector to D1 and observe the following results:

•	The TCC releases

•	The transmission immediately downshifts to First gear immediately

•	The engine slows the vehicle down

1. With the gear selector in D4, accelerate to Fourth gear with the TCC applied.
2. Release the accelerator pedal and lightly apply the brakes. Observe the following results:

•	The TCC releases.

•	Downshifts occur at speeds shown on the Shift Speed Chart. Refer to Shift Speed .

The shift solenoids control the upshifts in the manual gear ranges.

Perform the following tests by accelerating at 10-15 degrees TPS.

Manual Third (D3)

With the vehicle stopped, move the gear selector to D3 and accelerate in order to observe the following conditions:

Manual Second (D2)

Manual First (D1)

With the vehicle stopped, move the gear selector to D1. Accelerate to 32 km/h (20 mph) and observe the following conditions:

Reverse (R)

With the vehicle stopped, move the gear selector to R and slowly accelerate in order to observe that the 1-2 Shift Solenoid valve is ON.