DTC U0127: Lost Communication With Tire Pressure Monitor Control Module And/Or Keyless Entry Control Module

DTC detecting condition: 

No data is received from TPMS & keyless entry control module.

Trouble symptom: 

Keyless entry does not operate normally.

1. CHECK CAN COMMUNICATION HARNESS  .

   Perform the basic diagnostic procedure to check for fault in CAN communication harness. Ref. to LAN SYSTEM (DIAGNOSTICS)>Basic Diagnostic Procedure .

   Was the basic diagnostic procedure performed up to step 7?

   Yes: Go to  2 .

   No: Perform the basic diagnostic procedure. Ref. to LAN SYSTEM (DIAGNOSTICS)>Basic Diagnostic Procedure .

2. CHECK DTC (OTHER THAN U-CODE)  .

   Check the displayed DTC.

   Are DTCs other than U*** displayed?

   Yes: Perform the diagnosis for DTCs other than the displayed U-code.

   No: Go to  3 .

3. CHECK DTC (CURRENT MALFUNCTION)  .

   Check the displayed DTC.

   Is U0127 a current malfunction?

   Yes: Go to  4 .

   No: Go to  6 .

4. CHECK DTC (CURRENT MALFUNCTION)  .
   1. Check CAN communication circuit. Ref. to LAN SYSTEM (DIAGNOSTICS)>CAN Communication Circuit Check .
   2. Read the DTC using Subaru Select Monitor. Ref. to LAN SYSTEM (DIAGNOSTICS)>Read Diagnostic Trouble Code (DTC) .

   Is U0127 a current malfunction?

   Yes: Go to  5 .

   No: Go to  6 .

5. CHECK DTC  .

   Using the Subaru Select Monitor, read DTC of all the systems. Ref. to LAN SYSTEM (DIAGNOSTICS)>Read Diagnostic Trouble Code (DTC) .

   Is U0127 detected in the body integrated unit?

   Yes: Replace the TPMS & keyless entry control module. Ref. to WHEEL AND TIRE SYSTEM>TIRE PRESSURE MONITORING SYSTEM .

   No: Replace the module that the DTC has been detected.

6. CHECK HARNESS  .
   1. Shake the harness, and check for poor contact.
   2. Read the DTC using Subaru Select Monitor. Ref. to LAN SYSTEM (DIAGNOSTICS)>Read Diagnostic Trouble Code (DTC) .

   Is U0127 a current malfunction?

   Yes: Repair the poor contact of harness, or replace the harness.

   No: Go to  7 .

7. CHECK CONNECTOR  .

   Check the connector used for high speed CAN for poor contact.

   Is there poor contact of connector?

   Yes: Repair the connector that has poor contact, or replace harness.

   No: It is possible that temporary poor communication occurs. Delete the DTC.