NEXON 2.0 EV DTC Troubleshooting Document for VCU Version: 1.0 draft Date: 31-Jan-2022 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. U0121 - 08: - Lost Communication with ABS module - Bus Signal / Message Failures Overview: ISO Code U0121 - 08 Customer Symptom Vehicle is drivable but regeneration function can be affected Fault Effects (On Vehicle) Vehicle is drivable but regeneration function can be affected Lamp Status (If Any) No Indicator Fault Detection Condition ABS CAN messages are not received at VECU Normal Operating Condition ABS CAN message is received at VECU for vehicle operation Probable Trouble Area LV wiring Harness ABS fuse Healing Condition Ignition OFF wait till VCU sleeps & Ignition ON Component Details: Anti-Lock Braking System (ABS) ECU processes information from wheel-speed sensors and the hydraulic brake system to determine when to release braking pressure at a wheel that's about to lock up and start skidding. 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 ABS for damage (connectors, terminals bending & rusting of pins) 4. Check for loose connection of LV wiring harness between ABS and VCU 5. Check for damage to LV wiring harness connections between ABS and VCU Trouble Shooting: - Check for the ABS ECU supply pin and ignition pin connection from LV battery to ECU. (Refer schematic for details) Check for the LV wiring harness connection between VCU and ABS ECU on Vehicle CAN network as per the details given in LV schematic.
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