DTC P0756: Shift Solenoid "B" Performance/Stuck Off: Notes

WARNING: This page is about a different car, the 2022 Subaru WRX. However, it is still accessible from the selected car via links, so may be relevant.

1. -

DTC detecting condition:

Detected when two consecutive driving cycles with fault occur.

Trouble symptom:

Acceleration is poor during standing start.
Shift control malfunction

Wiring diagram:

CVT control system Ref. to WIRING SYSTEM>CVT CONTROL SYSTEM>WIRING DIAGRAM

Courtesy of SUBARU OF AMERICA, INC.

CAUTION:

Use the check board when measuring the TCM terminal voltage and resistance.
After servicing or replacing faulty parts, perform the last step of the basic diagnostic procedure. Ref. to TRANSMISSION (DIAGNOSTICS)>BASIC DIAGNOSTIC PROCEDURE

CHECK DTC .
Read the DTC of [Transmission] using the Subaru Select Monitor. Ref. to TRANSMISSION (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC)

Besides DTC P0756, is any of the DTCs P0973, P0974, P0976, P0977, P2747 and P2751 displayed?

Yes : Perform the diagnosis according to DTCs other than P0756. Ref. to TRANSMISSION (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC)>LIST

No : Go to 2.
CHECK PRIMARY DOWN SOLENOID (ACTIVE TEST) .
1. Turn the ignition switch to ON.
2. Using the Subaru Select Monitor, perform the active test for primary DOWN solenoid. Ref. to TRANSMISSION (DIAGNOSTICS)>ACTIVE TEST
Does the indication of 0 → 50% appear repeatedly during the active test, and does operating sound emit during indicating 50%?

Yes : Go to 5.

No : Go to 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
  
  (T1) No. 7 - Transmission body:
Is the resistance approximately 10 - 14.2 Ω? (When cold)

Yes : Go to 7.

No : Go to 4.
CHECK HARNESS .
Check the transmission harness. (Open circuit, short circuit to power supply, short circuit to ground, and poor contact)

Is the check result OK?

Yes : Go to 7.

No : Repair the harness.
CHECK TRANSMISSION FLUID .
1. Connect all connectors.
2. Check the amount of ATF. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR690)>CVTF>INSPECTION
Is the check result OK?

Yes : Go to 6.

No : Adjust the amount of ATF. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR690)>CVTF>INSPECTION Go to 6.
CHECK TRANSMISSION FLUID .
Check the condition of ATF. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR690)>CVTF>REPLACEMENT

Is the check result OK?

Yes : Return ATF. Go to 7.

No : Follow the "Corrective action" of ATF (CVTF) "CONDITION CHECK". Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR690)>CVTF>REPLACEMENT Go to 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. Using the Subaru Select Monitor, read data of [Actual line press.] in the [Data Monitor] of [Transmission]. Ref. to TRANSMISSION (DIAGNOSTICS)>DATA MONITOR
Is [Actual line press.] 0.5 - 1.5 MPa?

Yes : Go to 8.

No : Replace the transmission assembly. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR690)>TRANSMISSION ASSEMBLY
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. Using the Subaru Select Monitor, read data of [Actual Gear Ratio] in the [Data Monitor] of [Transmission]. Ref. to TRANSMISSION (DIAGNOSTICS)>DATA MONITOR
Is [Actual Gear Ratio] 2.0 - 2.7?

Yes : Go to 9.

No : Replace the transmission assembly. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR690)>TRANSMISSION ASSEMBLY
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. Using the Subaru Select Monitor, read data of [Actual Gear Ratio] in the [Data Monitor] of [Transmission]. Ref. to TRANSMISSION (DIAGNOSTICS)>DATA MONITOR
Is [Actual Gear Ratio] 0.5 - 1.3?

Yes : Go to 10.

No : Replace the transmission assembly. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR690)>TRANSMISSION ASSEMBLY
DRIVING CHECK BY INSPECTION MODE .
1. Using the Subaru Select Monitor, perform the clear memory of [Transmission]. Ref. to COMMON (DIAGNOSTICS)>CLEAR MEMORY
2. Execute the inspection mode. Ref. to TRANSMISSION (DIAGNOSTICS)>INSPECTION MODE
Does the AT OIL TEMP light blink and is DTC P0756 displayed?

Yes : Replace the transmission assembly. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR690)>TRANSMISSION ASSEMBLY

No : Current condition is normal. It is possible that temporary poor contact occurs.