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DTC P1894: CVT Gear Ratio Variation

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: 

Wiring diagram: 

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

G14613613Courtesy of SUBARU OF AMERICA, INC.
G14613630Courtesy of SUBARU OF AMERICA, INC.
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  
  1. CHECK DTC  .

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

    Is any DTC other than DTC P1894 displayed?

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

    And then, Go to  2.

    No  : Go to  2.

  2. CHECK TRANSMISSION FLUID  .
    NOTE:

    When ATF inspection is performed in the diagnosis for DTC other than DTC P1894, go to step   4 . 

    Check the amount of ATF. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR690)>CVTF>INSPECTION

    Is the check result OK?

    Yes  : Go to  3.

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

  3. CHECK TRANSMISSION FLUID  .

    Check the condition of ATF. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR690)>CVTF>REPLACEMENT

    Is the check result OK?

    Yes  : Go to  4.

    No  : Follow the "Corrective action" of ATF (CVTF) "CONDITION CHECK". Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR690)>CVTF>REPLACEMENT

  4. CHECK TCM INPUT SIGNAL (STALL TEST)  .
    1. Lift up the vehicle.
    2. Start the engine.
    3. Apply the parking brake.
    4. Set the select lever to "D" range.
    5. Depress the brake pedal firmly.
    6. Slowly open the accelerator fully, and stabilize the engine speed.
    7. Using the Subaru Select Monitor, read data of [Actual line press.] 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. 

    Is the value of [Actual line press.] 5.0 MPa or more?

    Yes  : Go to  5.

    No  : Replace the transmission assembly. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR690)>TRANSMISSION ASSEMBLY

  5. CHECK CONDITION AT STALL TEST  .

    Check the condition at stall test.

    Does the shock or noise occur at stall test?

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

    No  : Go to  6.

  6. DRIVING CHECK BY INSPECTION MODE  .
    1. Using the Subaru Select Monitor, perform the clear memory of [Transmission]. Ref. to COMMON (DIAGNOSTICS)>CLEAR MEMORY
    2. Execute the inspection mode. Ref. to TRANSMISSION (DIAGNOSTICS)>INSPECTION MODE 
      NOTE:

      Check FFD in advance, and slowly accelerate the vehicle under the same conditions (vehicle speed, oil temperature) as those when P1894 was recorded. If FFD was not saved, perform inspection mode D (including slow acceleration from a certain vehicle speed). 

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

    Is DTC P1894 displayed?

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

    No  : Go to  7.

  7. CHECK DATA DURING DRIVING (SECONDARY SPEED CHANGE)  .
    1. Start the engine.
    2. Reproduce the same conditions (vehicle speed, oil temperature) as those when P1894 was recorded.
    3. Using the Subaru Select Monitor, read the following data in the [Data Monitor] of [Transmission]. Ref. to TRANSMISSION (DIAGNOSTICS)>DATA MONITOR 
      • [Engine Speed]
      • [Actual Gear Ratio]
      • [Primary Rev Speed]
      • [Secondary Rev Speed]
      NOTE:

      Data at chain slippage 

      G14613656Courtesy of SUBARU OF AMERICA, INC.

    Is the value change of [Secondary Rev Speed] 100 rpm or more and 10 Hz or more?

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

    No  : Go to   8 .  If DTC P1894 is not detected, clear the memory to finish the diagnosis.

  8. 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. Set the select lever to "D" range.
    5. Drive at 2 km/h or more.
    6. Stop the vehicle.
    7. Shift the select lever to "P" range.
    8. Stabilize the engine speed at idle.
    9. Using the Subaru Select Monitor, read data of [Actual line press.], [Actual Secondary Pressure] in the [Data Monitor] of [Transmission]. Ref. to TRANSMISSION (DIAGNOSTICS)>DATA MONITOR 

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

    Is [Actual Secondary Pressure] 0.3 - 1.5 MPa?

    Yes  : Go to  9.

    No  : When the value of [Actual line press.] is out of range Go to  10.

    When the value of [Actual Secondary Pressure] is out of range Go to  22.

  9. CHECK INPUT SIGNAL FOR TCM  .
    1. Shift the select lever to "P" range.
    2. Keep the engine speed at 3, 000 rpm.
    3. Using the Subaru Select Monitor, read data of [Actual line press.], [Actual Secondary Pressure] in the [Data Monitor] of [Transmission]. Ref. to TRANSMISSION (DIAGNOSTICS)>DATA MONITOR 

    Are [Actual line press.] and [Actual Secondary Pressure] 1.5 - 2.5 MPa?

    Yes  : Currently, it is normal. Clear the memory to finish the diagnosis.

    No  : When the value of [Actual line press.] is out of range Go to  10.

    When the value of [Actual Secondary Pressure] is out of range Go to  22.

  10. CHECK LINE PRESSURE SOLENOID (ACTIVE TEST)  .
    1. Turn the ignition switch to ON.
    2. Using the Subaru Select Monitor, perform the active test for line pressure solenoid. Ref. to TRANSMISSION (DIAGNOSTICS)>ACTIVE TEST 

    Does the indication of 0 → 500 mA appear repeatedly during the active test, and does operating sound emit during indicating 500 mA?

    Yes  : Go to  13.

    No  : Go to  11.

  11. CHECK LINE PRESSURE SOLENOID  .
    1. Turn the ignition switch to OFF.
    2. Disconnect the TCM connector.
    3. Measure the resistance between TCM connector and transmission body. (While wiggling the harness)

      Connector & terminal 

      (B67) No. 32 - Transmission body:

    Is the resistance approximately 3.3 - 7.3 Ω? (When cold)

    Yes  : Go to  13.

    No  : Go to  12.

  12. CHECK HARNESS  .

    Check the transmission harness. (Open circuit, short circuit to power supply, short circuit to ground, and poor contact)

    Connector & terminal 

    (B67) No. 17 - (T35) No. 1:

    (B67) No. 4 - (T35) No. 2:

    (B67) No. 3 - (T35) No. 3:

    (B67) No. 32 - (T11) No. 1:

    Is the check result OK?

    Yes  : Go to  13.

    No  : Repair the harness.

  13. CHECK INPUT SIGNAL FOR TCM  .
    1. Turn the ignition switch to ON.
    2. Using the Subaru Select Monitor, read data of [Line Pressure Sensor Voltage.] in the [Data Monitor] of [Transmission]. (While shaking the line pressure sensor harness) Ref. to TRANSMISSION (DIAGNOSTICS)>DATA MONITOR 

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

    Yes  : Go to  21.

    No  : Go to  14.

  14. 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. (While wiggling the harness)

      Connector & terminal 

      (B67) No. 3 - (T35) No. 3:

      (B67) No. 4 - (T35) No. 2:

      (B67) No. 17 - (T35) No. 1:

    Is the resistance less than 1 Ω?

    Yes  : Go to  15.

    No  : Repair the open circuit of harness.

  15. CHECK HARNESS  .

    Measure the resistance between TCM connectors. (While wiggling the harness)

    Connector & terminal 

    (B67) No. 3 - (B67) No. 17:

    (B67) No. 4 - (B67) No. 3:

    (B67) No. 17 - (B67) No. 4:

    Is the resistance 1 MΩ or more?

    Yes  : Go to  16.

    No  : Repair the short circuit of harness.

  16. CHECK HARNESS  .

    Measure the resistance between TCM connector and transmission body. (While wiggling the harness)

    Connector & terminal 

    (B67) No. 3 - Transmission body:

    (B67) No. 4 - Transmission body:

    (B67) No. 17 - Transmission body:

    Is the resistance 1 MΩ or more?

    Yes  : Go to  17.

    No  : Repair the short circuit of harness.

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

      Connector & terminal 

      (B67) No. 17 (+) - (B67) No. 3 (-):

    Is the voltage 4.6 - 5.4 V?

    Yes  : Go to  18.

    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)

  18. 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 

      (B67) No. 17 (+) - (B67) No. 3 (-):

    Is the voltage 4.6 - 5.4 V?

    Yes  : Go to  19.

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

  19. CHECK LINE PRESSURE SENSOR OUTPUT  .

    Measure the voltage between TCM connectors.

    Connector & terminal 

    (B67) No. 4 (+) - (B67) 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  20.

  20. 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 (B67) and the line pressure sensor connector (T35).

    Is the check result OK?

    Yes  : Go to  21.

    No  : Repair the connector, or replace harness.

  21. CHECK TCM INPUT SIGNAL (STALL TEST)  .
    1. Connect all connectors.
    2. Adjust the amount of ATF. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR690)>CVTF>INSPECTION
    3. Lift up the vehicle.
    4. Start the engine.
    5. Apply the parking brake.
    6. Set the select lever to "D" range.
    7. Depress the brake pedal firmly.
    8. Slowly open the accelerator fully, and stabilize the engine speed.
    9. Using the Subaru Select Monitor, read data of [Actual line press.] 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. 

    Is the [Actual line press.] 6.0 MPa or more?

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

    No  : Replace the transmission assembly. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR690)>TRANSMISSION ASSEMBLY

  22. CHECK SECONDARY SOLENOID (ACTIVE TEST)  .
    1. Turn the ignition switch to ON.
    2. Using the Subaru Select Monitor, perform the active test for secondary solenoid. Ref. to TRANSMISSION (DIAGNOSTICS)>ACTIVE TEST 

    Does the indication of 0 → 500 mA appear repeatedly during the active test, and does operating sound emit during indicating 500 mA?

    Yes  : Go to  25.

    No  : Go to  23.

  23. CHECK SECONDARY SOLENOID  .
    1. Turn the ignition switch to OFF.
    2. Disconnect the TCM connector.
    3. Measure the resistance between TCM connector and transmission body. (While wiggling the harness)

      Connector & terminal 

      (B67) No. 46 - Transmission body:

    Is the resistance approximately 3.3 - 7.3 Ω? (When cold)

    Yes  : Go to  25.

    No  : Go to  24.

  24. CHECK HARNESS  .

    Check the transmission harness. (Open circuit, short circuit to power supply, short circuit to ground, and poor contact)

    Connector & terminal 

    (B67) No. 33 - (T34) No. 1:

    (B67) No. 5 - (T34) No. 2:

    (B67) No. 2 - (T34) No. 3:

    (B67) No. 46 - (T11) No. 4:

    Is the check result OK?

    Yes  : Go to  25.

    No  : Repair the harness.

  25. CHECK INPUT SIGNAL FOR TCM  .
    1. Turn the ignition switch to ON.
    2. Using the Subaru Select Monitor, read data of [secondary pressure sensor voltage.] in the [Data Monitor] of [Transmission]. (While shaking the secondary pressure sensor harness) Ref. to TRANSMISSION (DIAGNOSTICS)>DATA MONITOR 

    Is [secondary pressure sensor voltage.] 0.39 - 0.61 V?

    Yes  : Go to  33.

    No  : Go to  26.

  26. CHECK HARNESS  .
    1. Turn the ignition switch to OFF.
    2. Disconnect the TCM connector.
    3. Disconnect the secondary pressure sensor connector.
    4. Measure the resistance between TCM connector and secondary pressure sensor connector. (While wiggling the harness)

      Connector & terminal 

      (B67) No. 2 - (T34) No. 3:

      (B67) No. 5 - (T34) No. 2:

      (B67) No. 33 - (T34) No. 1:

    Is the resistance less than 1 Ω?

    Yes  : Go to  27.

    No  : Repair the open circuit of harness.

  27. CHECK HARNESS  .

    Measure the resistance between TCM connectors. (While wiggling the harness)

    Connector & terminal 

    (B67) No. 2 - (B67) No. 33:

    (B67) No. 5 - (B67) No. 2:

    (B67) No. 33 - (B67) No. 5:

    Is the resistance 1 MΩ or more?

    Yes  : Go to  28.

    No  : Repair the short circuit of harness.

  28. CHECK HARNESS  .

    Measure the resistance between TCM connector and transmission body. (While wiggling the harness)

    Connector & terminal 

    (B67) No. 2 - Transmission body:

    (B67) No. 5 - Transmission body:

    (B67) No. 33 - Transmission body:

    Is the resistance 1 MΩ or more?

    Yes  : Go to  29.

    No  : Repair the short circuit of harness.

  29. CHECK POWER SUPPLY FOR SECONDARY PRESSURE SENSOR  .
    1. Turn the ignition switch to ON.
    2. Measure the voltage between TCM connectors.

      Connector & terminal 

      (B67) No. 33 (+) - (B67) No. 2 (-):

    Is the voltage 4.6 - 5.4 V?

    Yes  : Go to  30.

    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)

  30. CHECK POWER SUPPLY FOR SECONDARY PRESSURE SENSOR  .
    1. Turn the ignition switch to OFF.
    2. Connect the secondary pressure sensor connector.
    3. Turn the ignition switch to ON.
    4. Measure the voltage between TCM connectors.

      Connector & terminal 

      (B67) No. 33 (+) - (B67) No. 2 (-):

    Is the voltage 4.6 - 5.4 V?

    Yes  : Go to  31.

    No  : Replace the secondary pressure sensor. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR690)>SECONDARY PRESSURE SENSOR

  31. CHECK SECONDARY PRESSURE SENSOR OUTPUT  .

    Measure the voltage between TCM connectors.

    Connector & terminal 

    (B67) No. 5 (+) - (B67) No. 2 (-):

    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  32.

  32. CHECK CONNECTOR  .
    1. Turn the ignition switch to OFF.
    2. Disconnect the TCM connector.
    3. Disconnect the secondary pressure sensor connector.
    4. Check the TCM connector (B67) and the secondary pressure sensor connector (T34).

    Is the check result OK?

    Yes  : Go to  33.

    No  : Repair the connector, or replace harness.

  33. CHECK TCM INPUT SIGNAL (STALL TEST)  .
    1. Lift up the vehicle.
    2. Start the engine.
    3. Apply the parking brake.
    4. Set the select lever to "D" range.
    5. Depress the brake pedal firmly.
    6. Slowly open the accelerator fully, and stabilize the engine speed.
    7. Using the Subaru Select Monitor, read data of [Actual Secondary 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. 

    Is the [Actual Secondary Pressure] 6.0 MPa or more?

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

    No  : Replace the transmission assembly. Ref. to CONTINUOUSLY VARIABLE TRANSMISSION (TR690)>TRANSMISSION ASSEMBLY

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