Line Pressure Check Procedure: Notes

Fig 1: Line Pressure Check

Courtesy of GENERAL MOTORS CORP.

CAUTION: Keep the brakes applied at all times in order to prevent unexpected vehicle motion. Personal injury may result if the vehicle moves unexpectedly.

NOTE: The total test running time should not be longer than 2 minutes. Running the test longer than 2 minutes may damage the transaxle.

Line pressures are calibrated for three sets of gear ranges - PARK, REVERSE and DRIVE. This allows the transmission line pressure to be appropriate for different pressure needs in different gear ranges. Refer to Line Pressure .

Before performing a line pressure check, verify that the line pressure control solenoid valve (SLT) for the transmission is receiving the correct electrical signal from the TCM:

Install the scan tool.
Start the engine and set the parking brake.
Check for diagnostic trouble codes, including the diagnostic code for a stored line pressure control solenoid valve.
Repair the vehicle if necessary. Include the following areas:
- Inspect the fluid level.
- Inspect the manual linkage at the transmission.
- Install or connect the scan tool.
- Install or connect the oil pressure gage at the line pressure tap.
Put the gear selector in PARK and set the parking brake.
Start the engine and allow the engine to warm up at idle.
Access the Line PC Solenoid - Functional Output Control on the scan tool.
Increase Line PC Sol. Ref. Current in 0.1 amp increments. Read the corresponding line pressure on the pressure gage. Allow the pressure to stabilize for 5 seconds after each current charge.
Compare your data to the Transmission in Park (P) Line Pressure specification table.
Firmly apply the brake and shift into REVERSE (R). Allow the engine to idle. Record the line pressure.
Increase the engine speed to 2450 RPM. Record the line pressure.
Compare your data to the Transmission in Reverse (R) Line Pressure specification table.
Firmly apply the brake and shift into DRIVE (D). Allow the engine to idle. Record the line pressure.
Increase the engine speed to 2450 RPM. Record the line pressure.
Compare your data to the Transmission in Drive (D) Line Pressure specification table.
Important: Before installing the fluid pressure test hole plug, apply LOCTITE^TM 242 thread sealer to the thread of the fluid pressure test hole plug.
Remove the oil pressure gage and install the fluid pressure test hole plug.

If your pressure readings differ greatly from the Line Pressure table, refer to the Diagnosis Tables contained in this section.

The scan tool is only able to control the line pressure control solenoid valve in PARK and NEUTRAL with the vehicle stopped. This protects the clutches from extremely high or low pressures in DRIVE or REVERSE ranges.

Refer to Line Pressure .

The pressures in the table assume an ATF temperature of 70°C (158°F). The pressure will vary with a change in temperature.