Subaru Legacy IV (2008 year). Manual - part 718

4AT(diag)-93

Diagnostic Procedure without Diagnostic Trouble Code (DTC)

AUTOMATIC TRANSMISSION (DIAGNOSTICS)

Step

Check

Yes

No

1

CHECK BODY INTEGRATED UNIT.
1) Turn the ignition switch to OFF.
2) Connect the Subaru Select Monitor to data 
link connector.
3) Turn the ignition switch to ON. (engine OFF)
4) Run the Subaru Select Monitor.
5) Read the data of “SPORT shift (buzzer)” of 
body integrated unit using Subaru Select Moni-
tor.

Is the SPORT shift buzzer dis-
play “ON”?

Replace the TCM. 
<Ref. to 4AT-61, 
Transmission Con-
trol Module 
(TCM).>

Go to step 2.

2

CHECK COMBINATION METER.
<Ref. to IDI-5, INSPECTION, Combination 
Meter System.>

Is the buzzer OK?

Refer to “Symp-
tom Related Diag-
nostic”. <Ref. to 
4AT(diag)-94, 
General Diagnos-
tic Table.>

Replace the com-
bination meter 
assembly. <Ref. to 
IDI-22, Combina-
tion Meter.>

4AT(diag)-94

General Diagnostic Table

AUTOMATIC TRANSMISSION (DIAGNOSTICS)

15.General Diagnostic Table

A: INSPECTION

Symptom

Problem parts

Starter does not operate when select lever is in “P” or “N” 
range. Starter operates when select lever is in “R” or “D” range.

• Inhibitor switch
• Select cable
• AT select lever
• Starter motor and harness

Abnormal noise when select lever is in “P” or “N”.

• Strainer
• Transfer duty solenoid
• Oil pump
• Drive plate
• ATF level too high or too low

Hissing noise occurs during standing start.

• Strainer
• ATF level too high or too low

Noise occurs while driving in “D1”.

• Final gear
• Planetary gear
• Reduction gear
• Differential gear oil level too high or too low

Noise occurs while driving in “D2”.

Noise occurs while driving in “D3”.

• Final gear
• Low & reverse brake
• Reduction gear
• Differential gear oil level too high or too low

Noise occurs while driving in “D4”.

• Final gear
• Low & reverse brake
• Planetary gear
• Reduction gear
• Differential gear oil level too high or too low

Vehicle moves when select lever is in “N” range.

• Select cable
• Inhibitor switch
• TCM
• Low clutch

Shock occurs when select lever is shifted from “N” to “D” range.

• Accelerator pedal position sensor
• ATF temperature sensor
• Line pressure linear solenoid
• Low clutch duty solenoid
• Low clutch
• TCM
• Harness
• Control valve
• ATF deterioration

Excessive time lag occurs when select lever is shifted from “N” 
to “D” range.

• Control valve
• Low clutch
• Line pressure linear solenoid
• Seal ring
• Front gasket of transmission case

Shock occurs when select lever is shifted from “N” to “R” range.

• Accelerator pedal position sensor
• ATF temperature sensor
• Line pressure linear solenoid
• TCM
• Harness
• Control valve
• ATF deterioration

Excessive time lag occurs when the select lever is shifted from 
“N” to “R” range.

• Control valve
• Low & reverse clutch
• Reverse clutch
• Line pressure linear solenoid
• Seal ring
• Front gasket of transmission case

4AT(diag)-95

General Diagnostic Table

AUTOMATIC TRANSMISSION (DIAGNOSTICS)

Vehicle does not start in any shift range. (Engine stalls)

• Parking brake mechanism
• Planetary gear

Vehicle does not start in any shift range. (Engine operates)

• Strainer
• Line pressure linear solenoid
• Control valve
• Drive pinion
• Hypoid gear
• Axle shaft
• Differential gear
• Oil pump
• Input shaft
• Output shaft
• Planetary gear
• Drive plate
• ATF level is too low
• Front gasket of transmission case

Vehicle does not start in “R” range only. (Engine operates)

• Select cable
• AT select lever
• Line pressure linear solenoid
• Control valve
• Low & reverse clutch
• Reverse clutch

Vehicle does not start in “R” range only. (Engine stalls)

• Low clutch
• 2-4 brake
• Planetary gear
• Parking brake mechanism

Vehicle does not start in “D” range. (Engine operates)

• Low clutch
• One-way clutch

Vehicle does not start in “D” range. (Engine stalls)

Reverse clutch

Vehicle does not start in “R” range only. (Engine operates)

Control valve

Acceleration during standing start is poor. (High rpm stall)

• Control valve
• Low clutch
• Reverse clutch
• ATF level is too low
• ATF deterioration
• Front gasket of transmission case
• Differential gear oil level too high or too low

Acceleration during standing start is poor. (Low rpm stall)

• Oil pump
• Torque converter one-way clutch
• Engine performance

Acceleration is poor when select lever is in “D” range. (Normal 
rpm stall)

• TCM
• Control valve
• High clutch
• 2-4 brake
• Planetary gear

Acceleration is poor when select lever is in “R” range. (Normal 
rpm stall)

• Control valve
• High clutch
• 2-4 brake
• Planetary gear

No shift occurs from 1st to 2nd gear.

• TCM
• Rear vehicle speed sensor
• Front vehicle speed sensor
• Accelerator pedal position sensor
• Control valve
• 2-4 brake

No shift occurs from 2nd to 3rd gear.

• TCM
• Control valve
• High clutch

Symptom

Problem parts

4AT(diag)-96

General Diagnostic Table

AUTOMATIC TRANSMISSION (DIAGNOSTICS)

No shift occurs from 3rd to 4th gear.

• TCM
• ATF temperature sensor
• Control valve
• 2-4 brake

Engine brake is not effected when select lever is shifted from 
4th gear to 3rd gear.

• Inhibitor switch
• TCM
• Accelerator pedal position sensor
• Control valve

Engine brake is not effected when select lever is shifted from 
3rd gear to 2nd gear.

Control valve

Engine brake is not effected when select lever is shifted from 
2nd gear to 1st gear.

• Control valve
• Low & reverse brake

Shift characteristics are erroneous.

• Inhibitor switch
• TCM
• Front vehicle speed sensor
• Rear vehicle speed sensor
• Accelerator pedal position sensor
• Control valve
• Ground

No lock-up occurs.

• TCM
• Accelerator pedal position sensor
• ATF temperature sensor
• Control valve
• Lock-up facing
• Engine speed signal

Parking brake does not function.

• Select cable
• AT select lever
• Parking mechanism

Shift lever cannot be moved or is hard to move from “P” range.

ATF spurts out.

ATF level too high

Differential oil spurts out.

Differential gear oil level too high

Differential oil level changes excessively.

• Seal pipe
• Double oil seal

Odor is produced from ATF supply pipe.

• High clutch
• 2-4 brake
• Low & reverse clutch
• Reverse clutch
• Lock-up facing
• ATF deterioration

Shock occurs when shifting from 1st to 2nd gear.

• TCM
• Torque converter turbine speed sensor
• Accelerator pedal position sensor
• 2-4 brake duty solenoid
• ATF temperature sensor
• Line pressure linear solenoid
• Control valve
• 2-4 brake
• ATF deterioration
• Engine performance
• Low & reverse duty solenoid

Slippage occurs when shifting from 1st to 2nd gear.

• TCM
• Accelerator pedal position sensor
• 2-4 brake duty solenoid
• ATF temperature sensor
• Line pressure linear solenoid
• Control valve
• 2-4 brake

Symptom

Problem parts