DTC U171F: Lost Lin Communication With Generator: Notes

1. - DTC detecting condition:

Immediately at fault recognition

Wiring diagram:

Charging System Ref. to WIRING SYSTEM>CHARGING SYSTEM .

Courtesy of SUBARU OF AMERICA, INC.

CAUTION:

Use the check board when measuring the ECM terminal voltage and resistance. Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>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) (H4DOTC)>Basic Diagnostic Procedure> PROCEDURE .

CHECK DTC .
1. Turn the ignition switch to ON.
2. 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>NOTE>BATTERY .
3. Measure the voltage of the generator B terminal.
  Connector & terminal
  
  Generator terminal B (+) - Engine ground (-):
  
  Is the voltage battery voltage?
  
  Yes : Go to 4.
  
  No : Check the generator B terminal harness and fuse.
CHECK HARNESS BETWEEN ECM AND GENERATOR CONNECTOR (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 & terminal
  
  (B134) No. 56 - (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 (H4DOTC)>GENERATOR .
  
  No : Repair the following item.
  - Open circuit of harness between ECM connector and generator
  - Poor contact of coupling connector
  - Poor contact of J/C