DTC P0841: Transmission Fluid Pressure Sensor/Switch "A" Circuit Range/Performance: Notes

DTC detecting condition: 

Detected when two consecutive driving cycles with fault occur.

Trouble symptom: 

• Acceleration is poor during standing start.
• Shift control malfunction
• Engine speed increases abruptly.

Wiring diagram: 

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

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK DTC  .

   Read the DTC using Subaru Select Monitor. Ref. to TRANSMISSION (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

   Besides DTC P0841, is DTC P0842 or P0843 displayed?

   Yes:  Perform the diagnosis according to DTC P0842 or P0843. Ref. to TRANSMISSION (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC)>LIST .

   No:  Go to  2.

2. CHECK DTC  .

   Read the DTC using Subaru Select Monitor. Ref. to TRANSMISSION (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

   Besides DTC P0841, is DTC P0746 or P0747 displayed?

   Yes:  Perform the diagnosis according to DTC P0746 or P0747. Ref. to TRANSMISSION (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC)>LIST .

   No:  Go to  3.

3. CHECK INPUT SIGNAL FOR TCM  .
   1. Turn the ignition switch to ON.
   2. Read the data of [Line Pressure Sensor Voltage.] using Subaru Select Monitor. (While shaking the line pressure sensor harness) Ref. to TRANSMISSION (DIAGNOSTICS)>DATA MONITOR .

   Is the value of [Line Pressure Sensor Voltage.] 0.39 - 0.61 V?

   Yes:  Go to  11.

   No:  Go to  4.

4. CHECK HARNESS  .
   CAUTION: Start work after ATF cools down.
   1. Turn the ignition switch to OFF.
   2. Disconnect the TCM connector.
   3. Remove the transmission oil pan.
   4. Disconnect the line pressure sensor connector.
   5. Measure the resistance between TCM connector and line pressure sensor connector.

      Connector & terminal 

      (B54) No. 3 - (AT2) No. 3:

      (B54) No. 4 - (AT2) No. 2:

      (B54) No. 17 - (AT2) No. 1:

   Is the resistance less than 1 Ω?

   Yes:  Go to  5.

   No:  Repair the open circuit of harness.

5. CHECK HARNESS  .

   Measure the resistance between TCM connectors.

   Connector & terminal 

   (B54) No. 3 - (B54) No. 17:

   (B54) No. 4 - (B54) No. 3:

   (B54) No. 17 - (B54) No. 4:

   Is the resistance 1 MΩ or more?

   Yes:  Go to  6.

   No:  Repair the short circuit of harness.

6. CHECK HARNESS  .

   Measure the resistance between TCM connector and transmission body.

   Connector & terminal 

   (B54) No. 3 - Transmission body:

   (B54) No. 4 - Transmission body:

   (B54) No. 17 - Transmission body:

   Is the resistance 1 MΩ or more?

   Yes:  Go to  7.

   No:  Repair the short circuit of harness.

7. CHECK LINE PRESSURE SENSOR POWER SUPPLY  .
   1. Turn the ignition switch to ON.
   2. Measure the voltage between TCM connectors.

      Connector & terminal 

      (B54) No. 17 (+) - (B54) No. 3 (-):

   Is the voltage 4.6 - 5.4 V?

   Yes:  Go to  8.

   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) .

8. CHECK LINE PRESSURE SENSOR POWER SUPPLY  .
   1. Turn the ignition switch to OFF.
   2. Connect the line pressure sensor connector.
   3. Turn the ignition switch to ON.
   4. Measure the voltage between TCM connectors.

      Connector & terminal 

      (B54) No. 17 (+) - (B54) No. 3 (-):

   Is the voltage 4.6 - 5.4 V?

   Yes:  Go to  9.

   No:  Replace the control valve body. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR690)>CONTROL VALVE BODY .

9. CHECK LINE PRESSURE SENSOR OUTPUT  .

   Measure the voltage between TCM connectors.

   Connector & terminal 

   (B54) No. 4 (+) - (B54) No. 3 (-):

   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 (TR690)>TRANSMISSION CONTROL MODULE (TCM) .

   No:  Go to  10.

10. CHECK CONNECTOR  .
    1. Turn the ignition switch to OFF.
    2. Disconnect the TCM connector.
    3. Disconnect the line pressure sensor connector.
    4. Check the TCM connector (B54) and the line pressure sensor connector (AT2).

    Is the check result OK?

    Yes:  Go to  11.

    No:  Repair the connector, or replace harness.

11. 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  12.

    No:  Adjust the amount of ATF. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR690)>CVTF>INSPECTION . Go to  12.

12. CHECK INPUT SIGNAL FOR TCM  .
    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 move the select lever to each range at an interval of 5 seconds.
       NOTE: Move the select lever in the following order: "P" → "R" → "N" → "D" → "N" → "R" → "P".
    4. Stabilize the engine speed at idle.
    5. Read the data of [Actual line press.] using Subaru Select Monitor. Ref. to TRANSMISSION (DIAGNOSTICS)>DATA MONITOR .

    Is [Actual line press.] 0.5 - 1.5 MPa?

    Yes:  Go to  13.

    No:  Replace the control valve body. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR690)>CONTROL VALVE BODY .

13. CHECK INPUT SIGNAL FOR TCM  .
    1. Shift the select lever to "P" range.
    2. Keep the engine speed at 3, 000 rpm.
    3. Read the data of [Actual line press.] using Subaru Select Monitor. Ref. to TRANSMISSION (DIAGNOSTICS)>DATA MONITOR .

    Is [Actual line press.] 1.5 - 2.5 MPa? And is the difference between the actual oil pressure and the value measured in Step  12 0.2 MPa or more?

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

    No:  Replace the control valve body. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR690)>CONTROL VALVE BODY .