Line Pressure Check

Line pressures are calibrated for two sets of gear ranges-Drive- Park-Neutral, and Reverse. This allows the transmission line pressure to be appropriate for different pressure needs in different gear ranges:
Before performing a line pressure check, verify that the pressure control solenoid for the transmission is receiving the correct electrical signal from the vehicle computer:
1. Hook up the scan tool.
2. Start the engine and set the parking brake.

CAUTION: Keep the brakes applied at all times in order to prevent unexpected vehicle motion.

3. Check for a P0748 malfunction code from the pressure control solenoid of the stored transmission. Check for other malfunction codes.
4. Repair the vehicle if necessary. Include the following areas:
^ Inspect the fluid level
^ Inspect the manual linkage at the transmission
^ Install the line pressure gage.

5. Put the gear selector in Park and set the parking brake.
6. Start the engine and allow the engine to warm up at idle.
7. Enter the diagnostics routine and select MISC TESTS.
8. Select A/T OUTPUTS-PC SOLENOID.
9. Increase the transmission fluid pressure by commanding low amperage. Read the corresponding line pressure on the pressure gage.
10. Compare your data to the Drive-Park-Neutral line pressure chart below. This line pressure is valid for PC solenoid overrides with the vehicle stopped at idle and in Park-Neutral.
If your pressure readings differ greatly from the line pressure chart, refer to Symptom Tables.

DYNAMIC LINE PRESSURE TESTING
The vehicle diagnostic overrides control the transmission pressure control solenoid:
^ In Park and neutral with the vehicle stopped at idle
^ In a dynamic mode during road testing

Under dynamic test conditions, you can override the solenoid's pressure signal in order to increase pressure from the normal PCM commanded pressure. During road test conditions, you can command high line pressures in order to verify a response from the line pressure system.
To verify the line Pressure response in the dynamic mode, access MISC. TESTS. Select A/T OUTPUTS-PC SOLENOID and drive the vehicle under normal road test conditions.
While driving the vehicle, depress the Up Arrow in order to gradually increase the transmission fluid pressure. As the transmission fluid pressure increases, transmission upshifts should become progressively harsher. This occurs because in this test mode line pressures are commanded which are higher than required.
If the pressure readings differ greatly from the Line Pressure specification, refer to Symptom Tables.