DTC U1821[86] Lost Communication With EHCU (BCM)

1. Body control system check

Refer to "64.Body Control 10I.Troubleshooting(BCM) diagnostic system check-body controls".

2. BCM DTC check

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

Yes

=>Go to EHCU communication verification.

No

Go to Intermittent conditions of body control system.

Refer to "223.Body Control 36D.Symptom(BCM) intermittent conditions of body 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 BCM replacement.

No

=>Go to Repair verification.

8. BCM replacement

Refer to "9.Body, Cab, Accessories 9Z.Body, Cab, Accessories Electrical Control BCM removal".

Refer to "9.Body, Cab, Accessories 9Z.Body, Cab, Accessories Electrical Control BCM installation".

Refer to "9.Body, Cab, Accessories 9Z.Body, Cab, Accessories Electrical Control BCM setting".

Procedure completion

=>Go to Repair verification.

9. Repair verification

1) Clear the DTC with a scan tool.

2) Turn OFF the ignition switch for 30 seconds or more.

3) Turn ON the ignition switch.

4) Observe the DTC information with a scan tool.