Line Pressure Test

WARNING: This page is about a different car, the 2005 Mercury Mountaineer and 2005 Ford Explorer. However, it is still accessible from the selected car via links, so may be relevant.

CAUTION: Carry out Line Pressure Test prior to carrying out Stall Speed Test. If line pressure is low at stall, do not carry out the Stall Speed Test or further transmission damage will occur. Do not maintain wide open throttle in any gear range for more than 5 seconds.

NOTE: Certain sensor failures may cause high PC, FMEM (Failure Mode Effect Management) actions. Be sure that self test and electrical repairs have been carried out or test results may be incorrect.

NOTE: The line pressure tap is used to verify output pressure from PC A or PC B by turning either one off while verifying the output from the other solenoid. The 2nd pressure tap is used to verify the output from the PC C solenoid.

This test verifies that the line pressure is within specifications.

Fig 1: Line Pressure Tap Location

Courtesy of FORD MOTOR CO.

Connect the pressure gauge to the line pressure tap.

Start the engine and check the line pressures. Refer to the following line pressure charts for the correct specification.

LINE PRESSURE CHART - 4.0L ENGINE

Range	Idle		WOT Stall
Range	PC C	Line	PCC	Line
R	758-862 kPa (110-125 psi)	965-1,551 kPa (140-225 psi)	758-862 kPa (110-125 psi)	2,000-2,482 kPa (290-360 psi)
N	0-103 kPa (0-15 psi)	758-1,034 kPa (110-150 psi)
(D) 3, 2, 1	0-103 kPa (0-15 psi)	758-1,034 kPa (110-150 psi)	0-103 kPa (0-15 psi)	1,448-1,793 kPa (210-260 psi)

LINE PRESSURE CHART - 4.6L ENGINE

Range	Idle		WOT Stall
Range	PCC	Line	PCC	Line
R	758-862 kPa (110-125 psi)	1,034-1,655 kPa (150-240 psi)	758-931 kPa (110-135 psi)	2,000-2,482 kPa (290-360 psi)
N	0-103 kPa (0-15 psi)	758-1,034 kPa (110-150 psi)
(D) 3, 2, 1	0-103 kPa (0-15 psi)	758-1,034 kPa (110-150 psi)	0-103 kPa (0-15 psi)	1,448-1,793 kPa (210-260 psi)

If the line pressure is not within specifications, check the PC C pressure.

Fig 2: Pressure Control (PC C) Tap Location
Courtesy of FORD MOTOR CO.
Connect the pressure gauge to the PC C pressure tap.
Start the engine and check the PC C pressure. Refer to line pressure diagnosis charts above for the correct specification.
If the PC C pressure is not within specification, GO to PINPOINT TEST D to diagnose PC C operation. If PC C operation is OK, refer to LINE PRESSURE DIAGNOSIS CHART for line pressure concern causes.

LINE PRESSURE DIAGNOSIS CHART

Test Results	Possible Source
High at Idle - All Ranges	Wiring Harnesses PC C Boost Valve PC C Solenoid Main Regulator Valve
Low at Idle - All Ranges	Low Fluid Level Fluid Inlet Filter/Seal Main Control Body Cross Leaks Gaskets Pump Separator Plate
Low - All Forward Ranges	Forward Clutch Main Control Overdrive Servo Intermediate Servo
Low in Park Only	Valve Body
Low in Reverse Only	Separator Plate Reverse Servo Piston, Cover Seal Reverse Clutch Overdrive Servo Intermediate Servo Valve Body Forward Clutch
Low in Neutral Only	Valve Body Overdrive Servo Intermediate Servo
Low in Overdrive Only	Forward Clutch Overdrive Servo Intermediate Servo Valve Body
Low in Drive Only (O/D Cancelled)	Forward Clutch Overdrive Servo Intermediate Servo Valve Body
Low in 1st Position	Forward Clutch Valve Body
Low in 2nd Position	Intermediate Servo Overdrive Servo Forward Clutch
Low in 3rd Position	Intermediate Servo Overdrive Servo Forward Clutch