Subaru Legacy BN/BS (2015-2019) Service Manual: Dtc p0756 shift solenoid "b" performance/stuck off

Subaru Legacy BN/BS (2015-2019) Service Manual / Continuously variable transmission (diagnostics) / Diagnostic procedure with diagnostic trouble code (dtc) / Dtc p0756 shift solenoid "b" performance/stuck off

DTC DETECTING CONDITION:

Detected when two consecutive driving cycles with fault occur.

TROUBLE SYMPTOM:

• Acceleration is poor during standing start.

• Shift control malfunction

1. ENGINE TYPE FB

WIRING DIAGRAM:

CVT control system CVT Control System > WIRING DIAGRAM

STEP	CHECK	YES	NO
1.CHECK DTC. Read the DTC using Subaru Select Monitor.	Besides DTC P0756, is any of the DTCs P0973, P0974, P0976, P0977, P2747 and P2751 displayed-	Perform the diagnosis according to DTCs other than P0756.	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0756 SHIFT SOLENOID "B" PERFORMANCE/STUCK OFF
2.CHECK PRIMARY DOWN SOLENOID (ACTIVE TEST). 1) Turn the ignition switch to ON. 2) Using the Subaru Select Monitor, perform forced operation of the primary DOWN solenoid. Active Test	Does the indication of 0 > 50% appear repeatedly during forced operation, and does operating sound emit during indicating 50%-	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0756 SHIFT SOLENOID "B" PERFORMANCE/STUCK OFF	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0756 SHIFT SOLENOID "B" PERFORMANCE/STUCK OFF
3.CHECK PRIMARY DOWN SOLENOID. 1) Turn the ignition switch to OFF. 2) Disconnect the TCM connector. 3) Measure the resistance between TCM connector and transmission body. Connector & terminal (T10) No. 30 — Transmission body:	Is the resistance approx. 10 — 13.5 -- (when cold)	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0756 SHIFT SOLENOID "B" PERFORMANCE/STUCK OFF	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0756 SHIFT SOLENOID "B" PERFORMANCE/STUCK OFF
4.CHECK HARNESS. Check the harness for continuity.	Is the harness normal- (Is it free from defects such as open circuit, power supply-output short or GND-output short circuit, or poor contact-)	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0756 SHIFT SOLENOID "B" PERFORMANCE/STUCK OFF	Repair the harness.
5.CHECK TRANSMISSION FLUID. 1) Connect the TCM connector. 2) Check the amount of ATF. CVTF > ADJUSTMENT	Is the ATF amount correct-	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0756 SHIFT SOLENOID "B" PERFORMANCE/STUCK OFF	Adjust the amount of ATF. CVTF > ADJUSTMENT
6.CHECK TRANSMISSION FLUID. Check the condition of ATF. CVTF > CONDITION CHECK	Is the ATF OK-	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0756 SHIFT SOLENOID "B" PERFORMANCE/STUCK OFF	Check according to the “Corrective action” of ATF (CVTF) “CONDITION CHECK”. CVTF > CONDITION CHECK
7.CHECK INPUT SIGNAL FOR TCM. 1) Lift up the vehicle. 2) Start the engine. 3) Warm up until the ATF temperature reaches to 40 — 70°C (104 — 158°F). 4) Depress the brake pedal, and shift the select lever to “D” range. 5) Shift the select lever to “P” range. 6) Stabilize the engine speed at idle. 7) Read the data of «Actual secondary pressure» using Subaru Select Monitor.	Is the «Actual secondary pressure» 0.5 — 1.5 MPa-	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0756 SHIFT SOLENOID "B" PERFORMANCE/STUCK OFF	Replace the transmission assembly. Automatic Transmission Assembly
8.CHECK INPUT SIGNAL FOR TCM. 1) Set the select lever to “D” range. 2) Release the brake pedal to stabilize the engine speed and front wheel speed. 3) Read the data of «Actual Gear Ratio» using Subaru Select Monitor.	Is the «Actual Gear Ratio» 1.5 — 2.6-	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0756 SHIFT SOLENOID "B" PERFORMANCE/STUCK OFF	Replace the transmission assembly. Automatic Transmission Assembly
9.CHECK INPUT SIGNAL FOR TCM. 1) Set the select lever to “D” range. 2) Slowly increase the speed to 40 km/h (25 MPH) and keep to a constant speed. 3) Read the data of «Actual Gear Ratio» using Subaru Select Monitor.	Is the «Actual Gear Ratio» 0.5 — 0.9-	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0756 SHIFT SOLENOID "B" PERFORMANCE/STUCK OFF	Replace the transmission assembly. Automatic Transmission Assembly
10.DRIVING CHECK BY INSPECTION MODE. 1) Turn the ignition switch to OFF. 2) Perform a drive check based on the “Inspection Mode”. Inspection Mode	Does the AT OIL TEMP light blink and is DTC P0756 displayed-	Replace the transmission assembly. Automatic Transmission Assembly	Current condition is normal. It is possible that temporary poor contact occurs.

2. ENGINE TYPE EZ

WIRING DIAGRAM:

CVT control system CVT Control System > WIRING DIAGRAM

STEP	CHECK	YES	NO
1.CHECK DTC. Read the DTC using Subaru Select Monitor.	Besides DTC P0756, is any of the DTCs P0973, P0974, P0976, P0977, P2747 and P2751 displayed-	Perform the diagnosis according to DTCs other than P0756.	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0756 SHIFT SOLENOID "B" PERFORMANCE/STUCK OFF
2.CHECK PRIMARY DOWN SOLENOID (ACTIVE TEST). 1) Turn the ignition switch to ON. 2) Using the Subaru Select Monitor, perform forced operation of the primary DOWN solenoid. Active Test	Does the indication of 0 > 50% appear repeatedly during forced operation, and does operating sound emit during indicating 50%-	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0756 SHIFT SOLENOID "B" PERFORMANCE/STUCK OFF	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0756 SHIFT SOLENOID "B" PERFORMANCE/STUCK OFF
3.CHECK PRIMARY DOWN SOLENOID. 1) Turn the ignition switch to OFF. 2) Disconnect the transmission connector. 3) Measure the resistance between transmission connector and transmission body. Connector & terminal (T4) No. 1 — Transmission body:	Is the resistance approx. 10 — 13.5 -- (when cold)	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0756 SHIFT SOLENOID "B" PERFORMANCE/STUCK OFF	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0756 SHIFT SOLENOID "B" PERFORMANCE/STUCK OFF
4.CHECK HARNESS. Check the harness for continuity.	Is the harness normal- (Is it free from defects such as open circuit, power supply-output short or GND-output short circuit, or poor contact-)	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0756 SHIFT SOLENOID "B" PERFORMANCE/STUCK OFF	Repair the harness.
5.CHECK TRANSMISSION FLUID. 1) Connect the transmission connector. 2) Check the amount of ATF. CVTF > ADJUSTMENT	Is the ATF amount correct-	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0756 SHIFT SOLENOID "B" PERFORMANCE/STUCK OFF	Adjust the amount of ATF. CVTF > ADJUSTMENT
6.CHECK TRANSMISSION FLUID. Check the condition of ATF. CVTF > CONDITION CHECK	Is the ATF OK-	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0756 SHIFT SOLENOID "B" PERFORMANCE/STUCK OFF	Check according to the “Corrective action” of ATF (CVTF) “CONDITION CHECK”. CVTF > CONDITION CHECK
7.CHECK INPUT SIGNAL FOR TCM. 1) Lift up the vehicle. 2) Start the engine. 3) Warm up until the ATF temperature reaches to 40 — 70°C (104 — 158°F). 4) Depress the brake pedal, and shift the select lever to “D” range. 5) Shift the select lever to “P” range. 6) Stabilize the engine speed at idle. 7) Read the data of «Actual secondary pressure» using Subaru Select Monitor.	Is the «Actual secondary pressure» 0.5 — 1.5 MPa-	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0756 SHIFT SOLENOID "B" PERFORMANCE/STUCK OFF	Replace the transmission assembly. Automatic Transmission Assembly
8.CHECK INPUT SIGNAL FOR TCM. 1) Set the select lever to “D” range. 2) Release the brake pedal to stabilize the engine speed and front wheel speed. 3) Read the data of «Actual Gear Ratio» using Subaru Select Monitor.	Is the «Actual Gear Ratio» 2.0 — 2.4-	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0756 SHIFT SOLENOID "B" PERFORMANCE/STUCK OFF	Replace the transmission assembly. Automatic Transmission Assembly
9.CHECK INPUT SIGNAL FOR TCM. 1) Set the select lever to “D” range. 2) Slowly increase the speed to 40 km/h (25 MPH) and keep to a constant speed. 3) Read the data of «Actual Gear Ratio» using Subaru Select Monitor.	Is the «Actual Gear Ratio» 0.5 — 0.8-	Diagnostic Procedure with Diagnostic Trouble Code (DTC) > DTC P0756 SHIFT SOLENOID "B" PERFORMANCE/STUCK OFF	Replace the transmission assembly. Automatic Transmission Assembly
10.DRIVING CHECK BY INSPECTION MODE. 1) Turn the ignition switch to OFF. 2) Perform a drive check based on the “Inspection Mode”. Inspection Mode	Does the AT OIL TEMP light blink and is DTC P0756 displayed-	Replace the transmission assembly. Automatic Transmission Assembly	Current condition is normal. It is possible that temporary poor contact occurs.

3. OUTLINE OF DIAGNOSIS (ENGINE TYPE FB)

• Detect the malfunction of shift-down fluid pressure control solenoid characteristics and hydraulic circuit characteristics (stuck to low pressure side).

• Judge as NG if the amount of gear rate change per second is within the predetermined value, even though the down-shift command is issued.

4. EXECUTION CONDITION (ENGINE TYPE FB)

Secondary Parameters	Execution condition
12 V battery system voltage	≥ 10 V
Engine speed	≥ 1000 rpm
Commanded duty of shift up pressure control solenoid	0%
Actual pulley ratio*	≥ 0.406
	and
	≤ 2.549

* Actual pulley ratio: Measured primary pulley shaft speed / Measured secondary pulley shaft speed

5. DIAGNOSTIC METHOD (ENGINE TYPE FB)

If the duration of time while the following conditions are met is longer than the time indicated, judge as NG.

Judgment Value

Malfunction Criteria	Threshold Value
Actual pulley ratio change for 1 second	> − 0.08
	and
	< 0.08
Commanded duty of shift down pressure control solenoid	> 80%

Time Needed for Diagnosis: 1 second

Malfunction Indicator Light Illumination: Illuminates when malfunction occurs in 2 continuous driving cycles.

6. OUTLINE OF DIAGNOSIS (ENGINE TYPE EZ)

• Detect the malfunction of shift-down fluid pressure control solenoid characteristics and hydraulic circuit characteristics (stuck to low pressure side).

• Judge as NG if the amount of gear rate change per second is within the predetermined value, even though the down-shift command is issued.

7. EXECUTION CONDITION (ENGINE TYPE EZ)

Secondary Parameters	Execution condition
12 V battery system voltage	≥ 10 V
Engine speed	≥ 1000 rpm
Commanded duty of shift up pressure control solenoid	0%
Actual pulley ratio*	≥ 0.363
	and
	≤ 2.348

* Actual pulley ratio: Measured primary pulley shaft speed / Measured secondary pulley shaft speed

8. DIAGNOSTIC METHOD (ENGINE TYPE EZ)

If the duration of time while the following conditions are met is longer than the time indicated, judge as NG.

Judgment Value

Malfunction Criteria	Threshold Value
Actual pulley ratio change for 1 second	> − 0.08
	and
	< 0.08
Commanded duty of shift down pressure control solenoid	> 80%

Time Needed for Diagnosis: 1 second

Malfunction Indicator Light Illumination: Illuminates when malfunction occurs in 2 continuous driving cycles.

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Inspection mode procedure
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