DTC U0420: Invalid Data Received From Power Steering Control Module

DTC detecting condition:

Invalid data was transmitted from power steering control module.

Trouble symptom:

Cooperation control with power steering control module does not operate properly.

CAUTION: Before performing diagnosis, refer to "CAUTION" in "General Description". Ref. to LAN SYSTEM (DIAGNOSTICS)>GENERAL DESCRIPTION>CAUTION .

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 .
CHECK DTC (OTHER THAN U-CODE) .
Check the displayed DTC.

Is DTC other than U*** displayed? (Current code)

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

No: Go to 3.
CHECK DTC (U-CODE) .
Check the displayed DTC.

Is DTC for the bus off or the data no-receive displayed? (Current code)

Yes: Perform the diagnosis for DTCs for the displayed bus off or the data no receive.

No: Go to 4.
CHECK DTC .
Check the displayed DTC.

Is DTC U0420 displayed? (Current code)

Yes: Go to 5.

No: Go to 7.
CHECK DTC .
1. Turn the ignition switch to OFF.
2. Disconnect the power steering control module connector.
3. Connect the disconnected connectors.
4. Turn the ignition switch to ON.
5. Using the Subaru Select Monitor, read all DTCs. Ref. to LAN SYSTEM (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .
Is DTC U0420 displayed? (Current code)

Yes: Go to 6.

No: Go to 7.
CHECK DTC .
Using the Subaru Select Monitor, read all DTCs. Ref. to LAN SYSTEM (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

Is DTC U0420 detected in several modules? (Current code)

Yes: Replace the power steering control module. Ref. to POWER ASSISTED SYSTEM (POWER STEERING)>POWER STEERING CONTROL MODULE .

No: Replace the module that the DTC has been detected.
CHECK HARNESS .
1. Shake the harness, and check for poor contact.
2. Using the Subaru Select Monitor, read all DTCs. Ref. to LAN SYSTEM (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .
Is DTC U0420 displayed? (Current code)

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

No: Go to 8.
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.