DTC U0401: Invalid Data Received From ECM/Pcm "A"

WARNING: This page is about a different variant/trim than selected.

DTC detecting condition:

Defective data from ECM.

Trouble symptom:

Defective data on CAN communication occurs.

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

CHECK CAN COMMUNICATION HARNESS .
Perform the basic diagnostic procedure to check for fault in CAN communication harness. Ref. to LAN SYSTEM (HEV)>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) (HEV)>BASIC DIAGNOSTIC PROCEDURE .
CHECK DTC (OTHER THAN U-CODE) .
Check the displayed DTC.

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

Yes : Perform the diagnosis for DTCs other than the displayed 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 malfunction)

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 U0401 displayed? (Current malfunction)

Yes : Go to 5.

No : Go to 7.
CHECK DTC .
1. Turn the ignition switch to OFF.
2. Disconnect the ECM connector.
3. Connect the disconnected connectors.
4. Using the Subaru Select Monitor, read all DTCs. Ref. to LAN SYSTEM (DIAGNOSTICS) (HEV)>DIAGNOSTIC TROUBLE CODE (DTC) .
Is DTC U0401 displayed? (Current malfunction)

Yes : Go to 6.

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

Is DTC U0401 detected in several modules? (Current malfunction)

Yes : Replace the ECM. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO (HEV))>ENGINE CONTROL MODULE (ECM) .

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) (HEV)>DIAGNOSTIC TROUBLE CODE (DTC) .
Is DTC U0401 displayed? (Current malfunction)

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.