DTC P0872: Transmission Fluid Pressure Sensor/Switch "C" Circuit Low: Notes

DTC detecting condition:

Immediately at fault recognition

Trouble symptom:

Shift characteristics malfunction

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 .

Wiring diagram:

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

Courtesy of SUBARU OF AMERICA, INC.

CHECK TCM INPUT SIGNAL (STALL TEST) .
1. Start the engine.
2. Warm up until the ATF temperature reaches to 40 - 70 °C (104 - 158 °F).
3. Depress the brake pedal, and shift the select lever to "D" range.
4. Drive for 1 minute at 64 km/h (40 MPH).
5. Stop the vehicle slowly.
6. Depress the brake pedal firmly with the select lever remaining in "D" range.
7. Slowly open the accelerator fully, and stabilize the engine speed.
8. Using the Subaru Select Monitor, read data of [Actual Primary Pressure] in the [Data Monitor] of [Transmission]. Ref. to TRANSMISSION (DIAGNOSTICS)>DATA MONITOR .
  CAUTION: Do not perform a stall test for 5 seconds or more at a time.
9. Release the accelerator pedal and shift the select lever to "P" range.
Is [Actual Primary Pressure] 0.1 - 3.4 MPa?

Yes: Check for poor contact of connector.

No: Go to 2.
CHECK HARNESS .
1. Turn the ignition switch to OFF.
2. Disconnect the TCM connector.
3. Disconnect the transmission connector.
4. Measure the resistance between TCM connector and transmission connectors.
  Connector & terminal
  
  (B67) No. 25 - (E33) No. 13:
  
  (B67) No. 8 - (E33) No. 19:
  
  (B67) No. 39 - (E33) No. 15:
Is the resistance less than 1 Ω?

Yes: Go to 3.

No: Repair the open circuit of harness.
CHECK HARNESS .
Measure the resistance between TCM connector and chassis ground.

Connector & terminal

(B67) No. 8 - Chassis ground:

(B67) No. 25 - Chassis ground:

Is the resistance 1 MΩ or more?

Yes: Go to 4.

No: Repair the short circuit of harness.
CHECK TRANSMISSION HARNESS .
1. Disconnect the primary pressure sensor connector.
2. Measure the resistance between transmission connector and primary pressure sensor connector.
Connector & terminal

(T2) No. 13 - (T43) No. 1:

(T2) No. 19 - (T43) No. 2:

(T2) No. 15 - (T43) No. 3:

Is the resistance less than 1 Ω?

Yes: Go to 5.

No: Repair the open circuit of harness.
CHECK TRANSMISSION HARNESS .
Measure the resistance between transmission connector and chassis ground.

Connector & terminal

(T2) No. 13 - Chassis ground:

(T2) No. 19 - Chassis ground:

Is the resistance 1 MΩ or more?

Yes: Go to 6.

No: Repair the short circuit of harness.
CHECK PRIMARY PRESSURE SENSOR POWER SUPPLY .
1. Connect the TCM connector.
2. Connect the transmission connector.
3. Turn the ignition switch to ON.
4. Measure the voltage between primary pressure sensor connector terminals.
  Connector & terminal
  
  (T43) No. 1 (+) - (T43) No. 3 (-):
Is the voltage 4.5 V or more?

Yes: Replace the primary pressure sensor. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION(TR690)>PRIMARY PRESSURE SENSOR . If the replacement of the sensor does not eliminate the malfunction, replace the TCM. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR690)>TRANSMISSION CONTROL MODULE (TCM) .

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) .