NEXON 3.0 EV DTC Troubleshooting Document for VCU Version: 2.0 Date: 22-Sep-2023 Copyright © TATA MOTORS Ltd. This document must not be used in anyway, such as copying and redistributing to third parties, without the consent of author. U1329 - 08: - Lost Communication with DCDC converter module - Bus Signal / Message Failures Overview: ISO Code U1329-08 Customer Symptom Vehicle is drivable Fault Effects (On Vehicle) The vehicle is drivable but Low Voltage battery charging will not happen Lamp Status (If Any) If LV battery is discharged below minimum threshold voltage, LV Battery charge lamp glows on cluster. Fault Detection Condition DC-DC Converter CAN messages are not received to VECU. Normal Operating Condition 3in1 combo - DC-DC Converter communicates to VECU via CAN protocol and is responsible to charge the LV battery, when vehicle is in crank mode or slow & fast charging is done on vehicle. Probable Trouble Area LV wiring Harness 3in1 combo - DC-DC Converter signal connector/terminals 3in1 combo - DC-DC Converter internal fault Healing Condition Ignition OFF wait till VCU sleeps & Ignition ON Component Details: HV DCDC Converter converts DC high voltage to low voltage to charge 12V battery. The conversion starts with enable signal to DCDC converter from VCU. Preliminary Checks: 1. Check for proper terminal connection of 12V LV Battery 2. Check LV Battery voltage to be in range (7.5V - 14V) 3. Check LV Supply Connection of 3in1 (KL30, 3in1 LV connector pin: 1) for damage (connectors, terminals bending & rusting of pins) 4. Check for loose connection of LV wiring harness between 3in1 and VCU 5. Check for damage to LV wiring harness connections between 3in1 and VCU
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