Line Pressure Test

WARNING: This page is about a different car, the 2009 Mercury Milan and 2009 Ford Fusion. 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 line pressure is low at stall, do not carry out the Stall Speed Test or further transaxle damage will occur. Do not maintain Wide Open Throttle (WOT) in any gear range for more than 5 seconds.

NOTE: Certain sensor failures may cause high line pressure as a result of failure mode effect management actions. Make sure that self-test and electrical repairs have been carried out, or test results may be incorrect.

This test verifies that the line pressure is within specifications.

Remove the line pressure port plug.

Fig 1: Locating Line Pressure Port Plug

Courtesy of FORD MOTOR CO.

Install a 1/8 x 28-to-1/8 x 28 pipe thread adapter into the line pressure tap.
- Tighten to 12 Nm (106 lb-in).

Fig 2: Locating Line Pressure Tap

Courtesy of FORD MOTOR CO.

Connect the Transmission Fluid Pressure Gauge to the adapter.
Start engine and check line pressures. Refer to the following Line Pressure Chart to determine if line pressure is within specifications.
If line pressure is not within specification, refer to Line Pressure Diagnosis Chart for line pressure concern causes.
When line pressure testing is complete, remove adapter and install line pressure port plug.
- Tighten to 8 Nm (71 lb-in).

LINE PRESSURE CHART

Range	Idle		Stall
P, N	345-450 kPa	50-65 psi	-	-
R	450-585 kPa	65-85 psi	1,930-2,310 kPa	280-335 psi
D, L	345-450 kPa	50-65 psi	1,240-1,450 kPa	180-210 psi

LINE PRESSURE DIAGNOSIS CHART

Test Results	Possible Source
Low pressure in all ranges	Worn pump.
Low pressure in all ranges	Transmission fluid leaking from pump, main control valve body or transaxle case.
Low pressure in all ranges	Pressure control solenoid inoperative.
Low pressure in all ranges	Solenoid regulating valve sticking.
Low pressure in D, L only	Transmission fluid leaking from forward clutch hydraulic circuit.
Low pressure in L	Transmission fluid leaking from intermediate/overdrive band hydraulic circuit.
Low pressure in L, R only	Transmission fluid leaking from low/reverse clutch hydraulic circuit.
Low in R only	Transmission fluid leaking from reverse clutch hydraulic circuit.
High pressure in all ranges	Pressure control solenoid inoperative or open wire harness.
High pressure in all ranges	Pressure regulator valve sticking.
High pressure in all ranges	Transmission Control Module (TCM) inoperative.