X104 CNG (Nexon) 4” Instrument Cluster DTC Troubleshooting Data Version: 2.0 Date: 19-August-24 Author: Suraj Shivsharan Page: 98 of 160 Copyright © TATA MOTORS Ltd. This document must not be used in any way, such as copying and redistributing to third parties, without the consent of author. U0028-88:- Vehicle Communication Bus A-Bus off Overview:- ISO Code U0028-88 Customer Symptom EPAS lamp ON , CE Lamp ON,MIL Lamp ON,ABS Lamp ON,TCM Lamp ON,SRS Lamp ON,EBD Lamp ON Fault Effects (On Vehicle) Default steering assistance, ECM will go into default mode, ABS degraded functionality, TCM degraded functionality Lamp Status (If Any) EPAS lamp ON , CE Lamp ON,MIL Lamp ON,ABS Lamp ON,TCM Lamp ON,SRS Lamp ON,EBD Lamp ON Fault Detection Condition Short circuit between CAN_H -CAN_L, CAN_H -GND, CAN_L-Battery lines. This DTC may also get logged in case of CANH OR CAN L open circuit. Normal Operating Condition ECU communicates properly with all ECUs. Probable Trouble Area CAN_H and CAN_L wires Healing Condition Removal of the above mentioned shorts/open in the wiring harness or at ECU pin. Trouble Shooting:- Start Read IVN DTCs in IPC If bus off and/or error passive DTC is logged in IPC in current state? No (In history) 1.Remove IPC ECU from vehicle wiring harness. 2.Measure the resistance between following lines in IPC vehicle side wiring harness. CANH &CANL,CANH & Ground, CANL & Battery ,CANH &Battery and CANL &Ground. Is resistance >10ohm ? Check the resistance between CANH(pin no.6) and CANL(pin no.5) of IPC connector in vehicle wiring harness.(with EMS connected on vehicle) Clear DTC Stop There is short circuit failure in between those two lines Do necessary repair in the harness Yes Yes No Is resistance ≠120ohm ? Yes Check the continuity between CANH(pin no.6) &CANL(pin no.5) lines of IPC and EMS vehicle side connector Do necessary repair in the harness No (120ohm) U0028-13 -Vehicle Communication Bus A-open circuit AND/OR U0028-88 -Vehicle Communication Bus A-Bus off
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