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:
Gear Range | Line Pressure Range |
|---|---|
Drive, Park or Neutral | Minimum line 50-55 psi, Maximum line 230-250 psi |
Reverse | Minimum line 90 psi, Maximum line 300 psi |
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:
- Hook up the scan tool.
- Start the engine and set the parking brake.
- Check for a P0748 malfunction code from the pressure control solenoid of the stored transmission. Check for other malfunction codes.
- Repair the vehicle if necessary. Include the following areas:
- Put the gear selector in Park and set the parking brake.
- Start the engine and allow the engine to warm up at idle.
- Enter the diagnostics routine and select MISC TESTS.
- Select A/T OUTPUTS-PC SOLENOID.
- Increase the transmission fluid pressure by commanding low amperage. Read the corresponding line pressure on the pressure gage.
- 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.
Caution: Keep the brakes applied at all times in order to prevent unexpected vehicle motion. Personal injury may result if the vehicle moves unexpectedly.
| • | Inspect the fluid level |
| • | Inspect the manual linkage at the transmission |
| • | Install the line pressure gage. |
If your pressure readings differ greatly from the line pressure chart, refer to Symptom Tables.
