Refer to "54.Brake Control 4A.Troubleshooting(ABS/ESC) diagnostic System Check - Brake Controls".
1) Turn OFF the ignition switch.
2) Connect the scan tool.
3) Turn ON the ignition switch.
4) Observe the DTC information for the rear differential lock control unit with a scan tool. Is a DTC set?
Yes
Go to the applicable DTC diagnosis.
No
1) Clear the DTC with a scan tool.
2) Turn OFF the ignition switch.
3) Start the engine.
4) Observe the DTC information with a scan tool.