DTC U0121[00] (Flash Code 34) Lost Communication With Anti-Lock Brake System (ABS) Control Module (Headlight Automatic Leveling Control)

1. Headlight auto leveling system check

Refer to "65.Lighting Control 10J.Troubleshooting(Headlight Automatic Leveling Control) diagnostic system check-headlight auto leveling controls".

2. Headlight auto leveling control unit DTC check

1) Observe whether a DTC is set in the headlight auto leveling control unit on the scan tool. Is a DTC set in the BCM?

Yes

=>Go to EHCU communication verification.

No

Go to Intermittent conditions of lighting control system.

Refer to "224.Lighting Control 37D.Symptom(Headlight Automatic Leveling Control) intermittent conditions of lighting control system".

3. EHCU communication verification

1) Use the scan tool to communicate with the EHCU and display the data. Can communication with the EHCU be established?

Yes

=>Go to EHCU DTC check.

No (Models with radar sensors/stereo cameras)

Refer to "54.Brake Control 4A.Troubleshooting(ABS/ESC) lost communication with the EHCU (models with radar sensor/ stereo camera)".

No (Models without radar sensors and stereo cameras)

Refer to "54.Brake Control 4A.Troubleshooting(ABS/ESC) lost communication with the EHCU (models without radar sensor and stereo camera)".

4. EHCU DTC check

1) Observe whether a DTC is set in the EHCU on the scan tool. Is a DTC set in the EHCU?

Yes

Go to the applicable DTC diagnosis.

No (Models with radar sensors/stereo cameras)

=>Go to Chassis CAN communication circuit and Body CAN communication circuit inspection.

No (Models without radar sensors and stereo cameras)

=>Go to CAN communication system inspection.

5. Chassis CAN communication circuit and Body CAN communication circuit inspection

1) Perform Chassis CAN communication circuit inspection and Body CAN communication circuit inspection.

Refer to "64.Body Control 10I.Troubleshooting(Central GateWay) chassis CAN communication circuit inspection".

Refer to "64.Body Control 10I.Troubleshooting(Central GateWay) body CAN communication circuit inspection".

Procedure completion

=>Go to Current DTC check.

6. CAN communication system inspection

1) Inspect the CAN communication system.

Refer to "51.Engine Control 1A.Troubleshooting(4JJ3 with DPD) scan tool does not communicate with CAN device (models without radar sensor and stereo camera)".

Refer to "51.Engine Control 1A.Troubleshooting(4JJ3 without DPD) scan tool does not communicate with CAN device (models without radar sensor and stereo camera)".

Refer to "51.Engine Control 1A.Troubleshooting(RZ4E-TC) scan tool does not communicate with CAN device (models without radar sensor and stereo camera)".

Procedure completion

=>Go to Current DTC check.

7. Current DTC check

1) Connect the scan tool.

2) Turn OFF the ignition switch.

3) Turn ON the ignition switch.

4) Observe the DTC information with a scan tool. Is a DTC set?

Yes

=>Go to EHCU replacement.

No

=>Go to Repair verification.

8. EHCU replacement

Refer to "4.Brakes 4Z.Brake Electrical Control EHCU removal".

Refer to "4.Brakes 4Z.Brake Electrical Control EHCU installation".

Refer to "4.Brakes 4Z.Brake Electrical Control EHCU setting".

Procedure completion

=>Go to Repair verification.

9. Repair verification

1) Clear the DTC with a scan tool.

2) Turn OFF the ignition switch.

3) Turn ON the ignition switch.

4) Observe the DTC information with a scan tool.