Q5/X451 FATC DTC Troubleshooting Data Version: 1.0 Date: 16-Oct-2018 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. Author: ERC Page: 164 of 202 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) 1) The HVAC outputs (motors and compressor request signal) should be functional using default data values where CAN data not available. For Default values refer the CAN communication matrix (dbc or function net file)]. 2) Error frames is observe on CAN bus during the Bus Off condition. 3) CAN communication is normal. 4) Vehicle communication bus "A" Bus Off DTC is in passive state in fault memory. 5) The HVAC outputs (motors and compressor request signal) is respond to the panel request. Fault Detection Condition Short circuit between CAN_H -CAN_L, CAN_H -GND, CAN_LVbatt 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.
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