Line Pressure Test

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 (WOT) 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 second pressure tap is used to verify the output from the PC C solenoid.

This test verifies that the line pressure is within specifications.

Connect pressure gauge to the line pressure tap.

Fig 1: Connecting Pressure Gauge To Line Pressure Tap
Courtesy of FORD MOTOR CO.

Start engine and check line pressures. Refer to the following LINE PRESSURE CHART to determine if line pressure is within specifications.

LINE PRESSURE CHART - 3.9L ENGINE

Range	Idle Pressure		WOT Stall Pressure
Range	PC C	Line	PC C	Line
P/N	0-69 kPa (0-10 psi)	483-620 kPa (70-90 psi)	0-69 kPa (0-10 psi)	483-620 kPa (70-90 psi)
R	345-414 kPa (50-60 psi)	689-827 kPa (100-120 psi)	2,151-2,289 kPa (312-332 psi)	2,151-2,289 kPa (312-332 psi)
D5	0-69 kPa (0-10 psi)	689-827 kPa (100-120 psi)	0-69 kPa (0-10 psi)	1,482-1,620 kPa (215-235 psi)
D4	0-69 kPa (0-10 psi)	689-827 kPa (100-120 psi)	0-69 kPa (0-10 psi)	1,482-1,620 kPa (215-235 psi)
M5/M4	0-69 kPa (0-10 psi)	689-827 kPa (100-120 psi)	0-69 kPa (0-10 psi)	1,482-1,620 kPa (215-235 psi)
M3	0-69 kPa (0-10 psi)	689-827 kPa (100-120 psi)	0-69 kPa (0-10 psi)	1,482-1,620 kPa (215-235 psi)
M2/M1	0-69 kPa (0-10 psi)	689-827 kPa (100-120 psi)	0-69 kPa (0-10 psi)	1,482-1,620 kPa (215-235 psi)

If line pressure is not within specifications, check PCC pressure.
Connect Pressure Gauge to PCC pressure tap.

Fig 2: Connecting Pressure Gauge To PCC Pressure Tap
Courtesy of FORD MOTOR CO.
Start engine and check PCC pressure. Refer to LINE PRESSURE DIAGNOSIS CHART in this article for specification.
If PCC pressure is not within specification, GO to PINPOINT TEST D to diagnose PCC operation. If PCC operation is OK, refer to LINE PRESSURE DIAGNOSIS CHART in this article 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 Rear 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 D5 Only	Forward Clutch Overdrive Servo Intermediate Servo Valve Body
Low in D4 Only (O/D Cancelled)	Forward Clutch Overdrive Servo Intermediate Servo Valve Body
Low in First Position	Forward Clutch Valve Body
Low in Second Position	Intermediate Servo Overdrive Servo Intermediate Servo Forward Clutch
Low in Third Position	Intermediate servo Overdrive servo Forward clutch