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Home >> Subaru >> 2017 >> Forester 2.0XT Touring >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 15 (Engine Control System (Diagnostics) (P2101 To U171F) (H4DO)) >> Diagnostic Procedure with Diagnostic Trouble Code (DTC) >> DTC U171F Lost Lin Communication With Generator >> Notes

DTC U171F Lost Lin Communication With Generator: Notes

WARNING: This page is about a different variant/trim than selected.

DTC detecting condition: 

Immediately at fault recognition

CAUTION:

Wiring diagram: 

Charging System Ref. to WIRING SYSTEM>Charging System .

Fig 1: Charging System Wiring Diagram (LIN Communication With Generator Lost)
G11272800Courtesy of SUBARU OF AMERICA, INC.
  1. CHECK DTC. 

    Check for DTC. Ref. to ENGINE (DIAGNOSTICS) (H4DO)>Read Diagnostic Trouble Code (DTC) .

    Is U171F displayed in [DTC]?

    • Yes: Go to  2.
    • No: Even if DTC is detected, the circuit has returned to a normal condition at this time. Reproduce the failure, and then perform the diagnosis.
  2. CHECK ECM CONNECTOR. 

    Check the connecting condition of ECM connector.

    Is the ECM connector correctly connected?

    • Yes: Go to  3.
    • No: Connect the ECM connector correctly.
  3. CHECK VOLTAGE OF GENERATOR B TERMINAL. 
    1. Turn the ignition switch to OFF.
    2. Disconnect the ground terminal from battery sensor. Ref. to NOTE>NOTE>BATTERY .
    3. Measure the voltage of the generator B terminal.

      Connector & terminal 

      Generator B terminal - Engine ground:

    Is it battery voltage?

    • Yes: Go to  4.
    • No: Check the generator B terminal harness and fuse.
  4. CHECK HARNESS BETWEEN ECM AND GENERATOR CONNECTOR. 
    1. Disconnect the connector from ECM.
    2. Disconnect the LIN communication connector from the generator.
    3. Measure the resistance of harness between ECM and generator LIN communication connector.

      Connector & terminal 

      (B134) No. 23 - (F26) No. 3:

    Is the resistance less than 1 Ω?

    • Yes: Check the connector for poor contact and check the harness. If no fault is found, replace the generator. Ref. to STARTING/CHARGING SYSTEMS(H4DO)>Generator .
    • No: repair the harness and connector.
      NOTE: In this case, repair the following item:
      • Open circuit of harness between ECM connector and generator
      • Poor contact of coupling connector