Line Pressure Test
WARNING: This page is about a different car, the 2019 Ford F-550 Super Duty, 2019 Ford F-450 Super Duty, 2019 Ford F-350 Super Duty, and 2019 Ford F-250 Super Duty. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
Carry out the Line Pressure Test prior to carrying out the Stall Speed Test. If the line pressure is low at idle, do not carry out the Stall Speed Test or further transmission damage can occur. Do not maintain Wide Open Throttle (WOT) in any transmission range for more than 5 seconds.
This test verifies that the line pressure is within specification.
- Connect the Transmission Fluid Pressure Gauge to the line pressure tap using an M10 X 1.00 fitting.NOTE: The line pressure tap is an M10 X 1.00 thread. Do not use a National Pipe Thread (NPT) fitting when installing a pressure gauge. If a NPT fitting is used, damage to the transmission case will occur.
- Start the engine and check the line pressure.
- Using a diagnostic scan tool, monitor and compare the PID LINEDSD# to actual measured pressure. Actual measured pressure should be within 10 PSI (69 kPa) of PID LINEDSD#. Raise engine RPM to 2000 RPM and verify LPC operation by monitoring LINE pressure while commanding LINEDSD# up and down.
- If the line pressure is not within specification, see the Line Pressure Diagnosis Chart for possible sources.
- When the pressure tests are complete, install the line pressure tap plug.
- Tighten to 11 Nm (97 lb-in).
Line Pressure Diagnosis Chart
| Test Results | Possible Source |
|---|---|
| HIGH at IDLE - ALL RANGES | Wiring Harnesses solenoid valve |
| LOW at IDLE - ALL RANGES | Fluid level low solenoid mechanically stuck off Fluid inlet filter/seal Main control Cross leaks Gaskets Separator plate Pump |
| LOW in Park ONLY | Main control |
| LOW in Reverse ONLY | Main control Low/reverse (1, R) clutch Direct (3, 5, R) clutch |
| LOW in Neutral ONLY | Main Control |
| LOW in DRIVE ONLY | Main control Low/reverse (1, R) clutch Forward (1, 2, 3, 4) clutch |
A no-drive condition can exist even with correct transmission fluid pressure because of inoperative clutches. Refer to the Clutch Application Chart to determine which clutch is applied in each gear range. A clutch concern can be further diagnosed by performing the air pressure test.