DTC U0121[00] EHCU Signal Timeout (Radar Sensor (Left))

1. Radar sensor system check

Refer to "75.Driver Assistance System 10W.Troubleshooting(Radar Sensor (Left)) Diagnostic system check-radar sensor system".

2. Current DTC check

1) Connect the scan tool.

2) Turn ON the ignition switch.

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

Yes

=>Go to EHCU communication verification.

No

Go to Intermittent conditions of radar sensor system.

Refer to "233.Driver Assistance System 46D.Symptom(Radar Sensor) intermittent conditions of radar sensor 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

Go to Lost communication with the EHCU.

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

4. EHCU DTC check

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

Yes

Go to the applicable DTC diagnosis.

No

=>Go to CAN communication circuit inspection.

5. CAN communication circuit inspection

1) Inspect the CAN communication circuit between the radar sensor (Left) (pins 2 and 5 of R41) and the EHCU (pins 14 and 26 of C13) for an open circuit or high resistance. Is the result normal?

Refer to "LHD Controller Area Network (Central Gateway C/U)" in the ETM (wiring diagram). (Open using the ETM viewer.).

Refer to "RHD Controller Area Network (Central Gateway C/U (4JJ3 with DPD))" in the ETM (wiring diagram). (Open using the ETM viewer.).

Refer to "RHD Controller Area Network (Central Gateway C/U (4JJ3 without DPD, RZ4E))" in the ETM (wiring diagram). (Open using the ETM viewer.).

Yes

=>Go to EHCU harness connector inspection.

No

Repair the connections as necessary.

=>Go to Repair verification.

6. EHCU harness connector inspection

1) Inspect for poor connections at the EHCU harness connector (pins 14 and 26 of C13). Is the connection status normal?

Refer to "LHD Controller Area Network (Central Gateway C/U)" in the ETM (wiring diagram). (Open using the ETM viewer.).

Refer to "RHD Controller Area Network (Central Gateway C/U (4JJ3 with DPD))" in the ETM (wiring diagram). (Open using the ETM viewer.).

Refer to "RHD Controller Area Network (Central Gateway C/U (4JJ3 without DPD, RZ4E))" in the ETM (wiring diagram). (Open using the ETM viewer.).

Yes

=>Go to Radar sensor (Left) harness connector inspection.

No

Repair the connections as necessary.

=>Go to Repair verification.

7. Radar sensor (Left) harness connector inspection

1) Inspect for poor connections at the radar sensor (Left) harness connector (pins 2 and 5 of R41). Is the connection status normal?

Refer to "LHD Controller Area Network (Central Gateway C/U)" in the ETM (wiring diagram). (Open using the ETM viewer.).

Refer to "RHD Controller Area Network (Central Gateway C/U (4JJ3 with DPD))" in the ETM (wiring diagram). (Open using the ETM viewer.).

Refer to "RHD Controller Area Network (Central Gateway C/U (4JJ3 without DPD, RZ4E))" in the ETM (wiring diagram). (Open using the ETM viewer.).

Yes

=>Go to EHCU replacement.

No

Repair the connections as necessary.

=>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. Current DTC follow-up check

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. Is a DTC set?

Yes

=>Go to Radar sensor (Left) replacement.

No

=>Go to Repair verification.

10. Radar sensor (Left) replacement

Refer to "9.Body, Cab, Accessories 9E.Instrumentation, Driver Info. radar sensor removal".

Refer to "9.Body, Cab, Accessories 9E.Instrumentation, Driver Info. radar sensor installation".

Refer to "9.Body, Cab, Accessories 9E.Instrumentation, Driver Info. radar sensor setting".

Procedure completion

=>Go to Repair verification.

11. 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.