Advanced Diagnostics

Advanced Diagnostics - DTC U1221 (35): Battery Condition Monitor (BCM) Module Lost Communication with DC-DC Converter






General Description
The battery condition monitor (BCM) module communicates with the DC-DC converter. When the communication information from the DC-DC converter is not received for a specified time, or when the received data is abnormal for a specified time or more, the BCM module detects a communication malfunction and stores a DTC.

Monitor Execution, Sequence, Duration, DTC Type, OBD Status






Enable Conditions






Malfunction Threshold
The communication information from the DC-DC converter is not received or the received data is abnormal for at least 2 seconds.

Diagnosis Details

Conditions for setting the DTC
When a malfunction is detected, the MIL comes on and a Pending DTC, a Confirmed DTC, and the freeze data are stored in the PCM and the BCM module memory.

Conditions for clearing the DTC
The MIL is cleared if the malfunction does not return in three consecutive trips in which the diagnostic runs. The MIL, the Pending DTC, the Confirmed DTC, and the freeze data can be cleared with the scan tool Clear command or by disconnecting the battery.