DTC P0966: Pressure Control Solenoid "B" Control Circuit Low: 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:

Immediately at fault recognition

Trouble symptom:

Excessive shift shock

Wiring diagram:

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

Courtesy of SUBARU OF AMERICA, INC.

CAUTION:

Use 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 F & R SOLENOID (WHEN THE ENGINE IS COLD: ATF TEMPERATURE APPROX. 20°C) .
1. Using the Subaru Select Monitor, check that [ATF Temp.] in [Data Monitor] of [Transmission] is 20°C. Ref. to TRANSMISSION (DIAGNOSTICS)>DATA MONITOR
2. Turn the ignition switch to OFF.
3. Disconnect the TCM connector.
4. Measure the resistance between TCM connector and transmission body.
  Connector & terminal
  
  (B67) No. 16 - Transmission body:
Is the resistance approximately 3.5 - 7.1 Ω?

Yes : Go to 2.

No : Go to 3.
CHECK F & R SOLENOID (WHEN THE ENGINE IS WARMED-UP: ATF TEMPERATURE 80°C OR MORE) .
1. Connect the TCM connector.
2. Using the Subaru Select Monitor, warm up the engine until [ATF Temp.] in [Data Monitor] of [Transmission] reaches 80°C or more. Ref. to TRANSMISSION (DIAGNOSTICS)>DATA MONITOR
3. Turn the ignition switch to OFF.
4. Disconnect the TCM connector.
5. Measure the resistance between TCM connector and transmission body.
  Connector & terminal
  
  (B67) No. 16 - Transmission body:
  
  NOTE:
  The resistance value increases as the temperature increases.
Is the resistance the same as the measured value in step 1 or less?

Yes : Go to 3.

No : Check for poor contact of connector, and if no fault is found, replace the TCM. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR690)>TRANSMISSION CONTROL MODULE (TCM)
CHECK HARNESS (GROUND SHORT CIRCUIT) .
1. Disconnect the transmission connector. (E34, T1)
2. Measure the resistance between TCM connector and chassis ground.
  Connector & terminal
  
  (B67) No. 16 - Chassis ground:
Is the resistance 1 MΩ or more?

Yes : Go to 4.

No : Repair or replace the harness.
CHECK HARNESS INSIDE TRANSMISSION .
CAUTION:
Start work after ATF cools down.
1. Remove the transmission oil pan.
2. Check for the harness pinch, damage.
Is the check result OK?

Yes : Go to 5.

No : Repair or replace the harness.
CHECK TRANSMISSION HARNESS (SHORT TO GROUND) .
1. Disconnect the control valve body connector.
2. Measure the resistance between transmission connector and chassis ground.
  Connector & terminal
  
  (T1) No. 12 - Chassis ground:
Is the resistance 1 MΩ or more?

Yes : Replace the control valve body. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR690)>CONTROL VALVE BODY

No : Repair or replace the harness.