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Home >> Subaru >> 2021 >> Crosstrek Hybrid >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 21 (Engine Control System (2.0L (Except For HEV)) (Diagnostics) (3 Of 4)) >> Diagnostic Procedure With Diagnostic Trouble Code (DTC) >> DTC P0851: Park/Neutral Switch Input Circuit Low >> CVT Model

CVT Model

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DTC detecting condition: 

Detected when two consecutive driving cycles with fault occur.

Trouble symptom: 

Improper idling

Wiring diagram: 

Engine Electrical System Ref. to WIRING SYSTEM (IMPREZA MODEL)>ENGINE ELECTRICAL SYSTEM>WIRING DIAGRAM . Ref. to WIRING SYSTEM (CROSSTREK MODEL (EXCEPT FOR HEV))>ENGINE ELECTRICAL SYSTEM>WIRING DIAGRAM .

G13614732Courtesy of SUBARU OF AMERICA, INC.
G13614733Courtesy of SUBARU OF AMERICA, INC.
CAUTION: Use the check board when measuring the ECM terminal voltage and resistance. Ref. to ENGINE (DIAGNOSTICS) (H4DO 2.0 (EXCEPT FOR HEV))>GENERAL DESCRIPTION>PREPARATION TOOL>HOW TO USE CHECK BOARD .
NOTE: After the faulty parts are repaired or replaced, perform the final check in Basic Diagnostic Procedure. Ref. to ENGINE (DIAGNOSTICS) (H4DO 2.0 (EXCEPT FOR HEV))>BASIC DIAGNOSTIC PROCEDURE>PROCEDURE .
  1. CHECK SELECT CABLE  .

    Check the select cable.

    Is there any fault in select cable?

    Yes:  Repair or adjust the select cable. Ref. to CONTROL SYSTEMS>SELECT CABLE .

    No:  Go to  2.

  2. CHECK INPUT SIGNAL OF ECM  .
    1. Turn the ignition switch to ON.
    2. Place the select lever in other than "P" range and "N" range.
    3. Measure the voltage between ECM connector and chassis ground.

    Connector and terminal 

    (B134) No. 39 (+) - Chassis ground (-):

    Is the voltage 10 V or more?

    Yes:  Repair the poor contact of ECM connector.

    No:  Go to  3.

  3. CHECK HARNESS BETWEEN ECM AND TRANSMISSION HARNESS CONNECTOR (SHORT TO GROUND)  .
    1. Turn the ignition switch to OFF.
    2. Disconnect the connector from ECM.
    3. Disconnect the connector from inhibitor switch.
    4. Measure the resistance between ECM connector and chassis ground.

    Connector and terminal 

    (B134) No. 39 - Chassis ground:

    Is the resistance 1 MΩ or more?

    Yes:  Replace the inhibitor switch.

    No:  Repair the short circuit to ground in harness between ECM connector and inhibitor switch connector.