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

WARNING: This page is about a different car, the 2021 Subaru Impreza. 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 (IMPREZA MODEL)>CVT CONTROL SYSTEM .

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) (IMPREZA MODEL)>BASIC DIAGNOSTIC PROCEDURE .

CHECK DTC .
Read the DTC of [Transmission] using the Subaru Select Monitor. Ref. to TRANSMISSION (DIAGNOSTICS) (IMPREZA MODEL)>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) (IMPREZA MODEL)>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) (IMPREZA MODEL)>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 TCM connector.
3. Measure the resistance between TCM connector and transmission body.
  Connector & terminal
  
  (T10) No. 30 - 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 the TCM connector.
2. Check the amount of ATF. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR580 IMPREZA)>CVTF>ADJUSTMENT .
Is the check result OK?

Yes: Go to 6.

No: Adjust the amount of ATF. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR580 IMPREZA)>CVTF>ADJUSTMENT .
CHECK TRANSMISSION FLUID .
Check the condition of ATF. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR580 IMPREZA)>CVTF>CONDITION CHECK .

Is the check result OK?

Yes: Go to 7.

No: Check according to the "Corrective action" of ATF (CVTF) "CONDITION CHECK". Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR580 IMPREZA)>CVTF>CONDITION CHECK .
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 Secondary Pressure] in the [Data Monitor] of [Transmission]. Ref. to TRANSMISSION (DIAGNOSTICS) (IMPREZA MODEL)>DATA MONITOR .
Is [Actual Secondary Pressure] 0.5 - 1.5 MPa?

Yes: Go to 8.

No: Replace the transmission assembly. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR580 IMPREZA)>AUTOMATIC 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) (IMPREZA MODEL)>DATA MONITOR .
Is [Actual Gear Ratio] 1.5 - 2.6?

Yes: Go to 9.

No: Replace the transmission assembly. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR580 IMPREZA)>AUTOMATIC 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) (IMPREZA MODEL)>DATA MONITOR .
Is [Actual Gear Ratio] 0.5 - 0.9?

Yes: Go to 10.

No: Replace the transmission assembly. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR580 IMPREZA)>AUTOMATIC TRANSMISSION ASSEMBLY .
DRIVING CHECK BY INSPECTION MODE .
1. Using the Subaru Select Monitor, perform the clear memory of [Transmission]. Ref. to COMMON (DIAG)>CLEAR MEMORY .
2. Execute the inspection mode. Ref. to TRANSMISSION (DIAGNOSTICS) (IMPREZA MODEL)>INSPECTION MODE .
Does the AT OIL TEMP light blink and is DTC P0756 displayed?

Yes: Replace the transmission assembly. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR580 IMPREZA)>AUTOMATIC TRANSMISSION ASSEMBLY .

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