DTC U171F: Lost Lin Communication With Generator: Notes

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

1. -

DTC detecting condition:

Immediately at fault recognition

Wiring diagram:

Charging System Ref. to WIRING SYSTEM (IMPREZA MODEL)>CHARGING SYSTEM>WIRING DIAGRAM . Ref. to WIRING SYSTEM (CROSSTREK MODEL (EXCEPT FOR HEV))>CHARGING SYSTEM>WIRING DIAGRAM .

IMPREZA MODEL

Courtesy of SUBARU OF AMERICA, INC.
CROSSTREK MODEL

Courtesy 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 .

CHECK DTC .
Using the Subaru Select Monitor or a general scan tool, read the DTC of [Engine]. Ref. to COMMON (DIAG)>DIAGNOSTIC TROUBLE CODE (DTC) .

Is DTC U171F displayed? (Current malfunction)

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 again.
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.
CHECK VOLTAGE OF GENERATOR B TERMINAL .
1. Turn the ignition switch to OFF.
2. Disconnect the ground terminal from battery sensor. Ref. to REPAIR CONTENTS>REPAIR CONTENTS>NOTE>BATTERY .
3. Measure the voltage of the generator B terminal.
  Connector and terminal
  
  Generator B terminal - Engine ground:
  
  Is it battery voltage?
  
  Yes: Go to 4.
  
  No: Check the generator B terminal harness and fuse.
CHECK HARNESS BETWEEN ECM AND GENERATOR (OPEN) .
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 and terminal
  
  (B134) No. 17 - (F26) No. 1:
  
  Is the resistance less than 1 Ω?
  
  Yes: Check the connector for poor contact and check the harness again. If no fault is found, replace the generator. Ref. to STARTING/CHARGING SYSTEMS (H4DO (EXCEPT FOR HEV))>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