DTC P0871: Transmission Fluid Pressure Sensor/Switch "C" Circuit Range/Performance: Notes

CAUTION:

Before performing diagnosis, record the freeze frame data.
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 .

DTC detecting condition:

Immediately at fault recognition

Trouble symptom:

Acceleration is poor during standing start.
Shift control malfunction
Engine speed increases abruptly.
CVT chain slippage

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

Is only DTC P0871 displayed?

Yes: Go to 4.

No: Go to 2.
CHECK DTC .
Read the DTC of [Transmission] using the Subaru Select Monitor. Ref. to TRANSMISSION (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

Is DTC P0872 or P0873 displayed?

Yes: Perform the diagnosis according to DTC P0872 or P0873. Ref. to TRANSMISSION (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC)>LIST .

No: Go to 3.
CHECK DTC .
Read the DTC of [Transmission] using the Subaru Select Monitor. Ref. to TRANSMISSION (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

Is DTC P0730, P0751, P0752, P0756, or P0757 displayed?

Yes: Perform the diagnosis according to DTC P0730, P0751, P0752, P0756 or P0757. Ref. to TRANSMISSION (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC)>LIST .

No: Go to 4.
CHECK INPUT SIGNAL FOR TCM .
1. With the engine stopped, soak for at least 5 minutes.
2. Turn the ignition switch to ON.
3. Using the Subaru Select Monitor, read data of [Primary Pressure Sensor Voltage.] in the [Data Monitor] of [Transmission]. (While shaking the primary pressure sensor harness) Ref. to TRANSMISSION (DIAGNOSTICS)>DATA MONITOR .
Is [Primary Pressure Sensor Voltage.] 0.39 - 0.61 V?

Yes: Go to 12.

No: 5.
CHECK HARNESS .
1. Turn the ignition switch to OFF.
2. Disconnect the TCM connector.
3. Disconnect the primary pressure sensor connector.
4. Measure the resistance between TCM connector and primary pressure sensor connector.
  Connector & terminal
  1. (B67) No. 25 - (T43) No. 1:
  2. (B67) No. 8 - (T43) No. 2:
  3. (B67) No. 39 - (T43) No. 3:
Is the resistance less than 1 Ω?

Yes: Go to 6.

No: Repair the open circuit of harness.
CHECK HARNESS .
Measure the resistance between TCM connectors.

Connector & terminal
1. (B67) No. 8 - (B67) No. 39:
2. (B67) No. 25 - (B67) No. 8:
3. (B67) No. 39 - (B67) No. 25:
Is the resistance 1 MΩ or more?

Yes: Go to 7.

No: Repair the short circuit of harness.
CHECK HARNESS .
Measure the resistance between TCM connector and transmission body.

Connector & terminal
1. (B67) No. 8 - Transmission body:
2. (B67) No. 25 - Transmission body:
3. (B67) No. 39 - Transmission body:
Is the resistance 1 MΩ or more?

Yes: Go to 8.

No: Repair the short circuit of harness.
CHECK PRIMARY PRESSURE SENSOR POWER SUPPLY .
1. Turn the ignition switch to ON.
2. Measure the voltage between TCM connectors.
Connector & terminal

(B67) No. 25 (+) - (B67) No. 39 (-):

Is the voltage 4.6 - 5.4 V?

Yes: Go to 9.

No: Check for poor contact of connector and for short circuit in harness between the 12 V power supply system. If no fault is found, replace the TCM. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION(TR690)>TRANSMISSION CONTROL MODULE (TCM) .
CHECK PRIMARY PRESSURE SENSOR POWER SUPPLY .
1. Turn the ignition switch to OFF.
2. Connect the primary pressure sensor connector.
3. Turn the ignition switch to ON.
4. Measure the voltage between TCM connectors.
Connector & terminal

(B67) No. 25 (+) - (B67) No. 39 (-):

Yes: Go to 10.

No: Replace the primary pressure sensor. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION(TR690)>PRIMARY PRESSURE SENSOR . If the replacement of the sensor do not eliminate the malfunction, replace the TCM. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION(TR690)>TRANSMISSION CONTROL MODULE (TCM) .
CHECK PRIMARY PRESSURE SENSOR OUTPUT .
Measure the voltage between TCM connectors.

Connector & terminal

(B67) No. 8 (+) - (B67) No. 39 (-):

Is the voltage 0.39 - 0.61 V?

Yes: Check for poor contact of connector, and if no fault is found, replace the TCM. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION(TR580)>TRANSMISSION CONTROL MODULE (TCM)

No: Go to 11.
CHECK CONNECTOR .
1. Turn the ignition switch to OFF.
2. Disconnect the TCM connector.
3. Disconnect the primary pressure sensor connector.
4. Check the TCM connector (B67) and the primary pressure sensor connector (T43).
Is the check result OK?

Yes: Go to 12.

No: Repair the connector, or replace 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: Replace the primary pressure sensor. Ref. to PRIMARY PRESSURE SENSOR . Go to 13.

No: Replace the primary pressure sensor, and adjust the amount of ATF. Ref. to PRIMARY PRESSURE SENSOR . Go to 13.
CHECK INPUT SIGNAL FOR TCM
1. Using the Subaru Select Monitor, perform the clear memory of [Transmission]. Ref. to COMMON (DIAGNOSTICS)>CLEAR MEMORY .
2. Start the engine.
3. Warm up until the ATF temperature reaches to 40 - 70 °C (104 - 158 °F).
4. Set the select lever to "D" range.
5. Drive at a constant speed of 30 km/h or more for one minute or more.
6. Stop the vehicle.
7. Shift the select lever to "P" range.
8. Read the DTC of [Transmission] using the Subaru Select Monitor. Ref. to TRANSMISSION (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .
Does the AT OIL TEMP light blink and is DTC P0871 displayed?

Yes: Replace the TCM. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION(TR690)>TRANSMISSION CONTROL MODULE (TCM) . If the replacement of TCM does not eliminate the malfunction, replace the transmission assembly. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION(TR690)>TRANSMISSION ASSEMBLY .

No: Current condition is normal. It is possible that temporary failure occurred to the primary pressure sensor.