Line Pressure

Line pressures are calibrated for 2 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. See LINE PRESSURE RANGE SPECIFICATIONS  table.

1. Install a scan tool.
2. Start the engine and set the parking brake.
3. Check for DTCs, including the DTC for a pressure control solenoid.
4. Repair the vehicle if necessary. Include the following areas:
   • Inspect the fluid level.
   • Inspect the manual linkage at the transmission.
5. Install or connect the scan tool.
6. Install or connect the Pressure Gauge (J-21867) at the line pressure tap. See Fig 1.
7. Put the gearshift lever in Park and set the parking brake.
8. Start the engine and allow the engine to warm up at idle.
9. Access the OVERRIDE PRESSURE CONTROL SOLENOID test on the scan tool.
10. Increase the Pressure Control (PC) solenoid current in 0.1 amp increments. Read the corresponding line pressure on the pressure gauge. Allow the pressure to stabilize for 5 seconds after each current change.
11. Compare your data to the line pressure specifications. See LINE PRESSURE SPECIFICATIONS  table.
12. Remove the pressure gauge.
13. Apply pipe thread sealant with Teflon (GM P/N 12346004) to the line pressure tap plug. Install the line pressure tap plug. Tighten plug to specification. See TORQUE SPECIFICATIONS .

If your pressure readings differ greatly from the line pressure table, see SYMPTOM DIAGNOSIS  under TROUBLE SHOOTING.

The scan tool is only able to control the pressure control solenoid in Park and Neutral with the vehicle stopped at idle. This protects the clutches from extremely high or low pressures in Drive or Reverse ranges.

Fig 1: Checking Line Pressure

Courtesy of GENERAL MOTORS CORP.