DTC U0122: Lost Communication With Vehicle Dynamics Control Module

DTC detecting condition: 

No data from VDC Control Module is received.

Trouble symptom: 

ABS warning light and VDC warning light illuminate.

1. CHECK CAN COMMUNICATION HARNESS. 

   Perform the basic diagnostic procedure to check for fault in CAN communication harness. Refer 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. Refer 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 U0122 a current malfunction?

   Yes:  Go to  4.

   No:  Go to  6.

4. CHECK DTC (CURRENT MALFUNCTION). 
   1. Check CAN communication circuit. Refer to LAN SYSTEM (DIAGNOSTICS)>CAN COMMUNICATION CIRCUIT CHECK .
   2. Read the DTC using Subaru Select Monitor. Refer to LAN SYSTEM (DIAGNOSTICS)>READ DIAGNOSTIC TROUBLE CODE (DTC) .

   Is U0122 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, Refer to LAN SYSTEM (DIAGNOSTICS)>READ DIAGNOSTIC TROUBLE CODE (DTC) .

   Is U0122 detected in several modules?

   Yes:  Replace the VDC Control Module. Refer to VEHICLE DYNAMICS CONTROL (VDC)>VDC CONTROL MODULE AND HYDRAULIC CONTROL UNIT (VDCCM & H/U) .

   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, Refer to LAN SYSTEM (DIAGNOSTICS)>READ DIAGNOSTIC TROUBLE CODE (DTC) .

   Is U0122 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 s possible that temporary poor communication occurs. Delete the DTC.