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.