Copyright © TATA MOTORS Ltd. This document must not be used in any w ay, such as copying and redistributing to third parties, w ithout the consent of author . SRS / Airbag ECU – DTC Troubleshooting Guide Vers ion: 14.0 Da te: 14-February-2017 Prepared by:Airbag COC Review & Approved by:Sanjeev VM Page: 202 of 549 U0028-88:- Vehicle Communication Bus A - Bus off Overview: ISO Code U0028-88 Customer Symptom All warning lamps will be ON Fault Effects (On Vehicle) 1.SRS (Airbag) Warning lamp functionality will be affected. 2.SBR Chime functionality will be affected. 3.Door unlock & hazard light functionality will be affected. Lamp Status (If Any) All warning lamps will be ON Fault Detection Condition 1. Short circuit between CAN_H (Pin A1) - CAN_L (PinA2), CAN_H – GND (Pins A7, 23), CAN_L - Vbat (Pin A12) lines. 2. Open circuit of CAN_H or/and CAN_L lines (in this case only RCM (SRS) warning lamp will be ON) Normal Operating Condition RCM (SRS) ECU should communicate properly with other ECU’s in the vehicle. Probable Trouble Area CAN_H and CAN_L wires (Wiring harness), ECU connectors, ECU pins. Healing Condition Removal of the above mentioned shorts or open conditions in the wiring harness or at ECU pin. Airbag Warning Lamp behavior for U0028-88 DTC:- U0028-88 IVN DTC is healed in the same IGN cycle; once corresponding failure detection conditions are not present. However, Airbag Warning Lamp (triggered due to this failure/DTC) will turn off in following two conditions. a. When above mentioned DTC is in healed state and Clear DTC command is sent; in this case Lamp will be OFF in same IGN cycle b. When above mentioned DTC is in healed state and IGN OFF/ON (1 time) operation is done. This is implemented as per supplier’s strategy. Component Details:- Airbag ECU:- It is fitted in the floor of central console in the car. The Airbag Electronic Control Unit (ECU) controls the deployment system to allow an appropriate igniting of the Airbags and belt pre-tensioners to restrain the driver and passengers. Preliminary Checks:- 1. Ensure the proper locking of Airbag ECU wiring harness connectors in the vehicle by the locking sound. 2. Check resistance between diagnostic CAN pin number 6 and 14 in OBD connector. It should be 120 ohm. 3. Check for short conditions between CAN_H-CAN_L, CAN_H-GND, CAN_L-GND, CAN_H-Vbat and CAN_LVbat. There should not be any short circuit conditions. 4. Check continuity between IPC CAN_H (pin no. 15) vehicle side connector to OBD connector CAN_H (pin no. 6) and CAN_L (pin no. 14) vehicle side connector to OBD connector CAN_L (pin no.14). 5. Read IVN DTCs in IPC in Ignition ON condition. Trouble Shooting:-
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