Q501 4 Cylinder MT Application DTC Troubleshooting Data Version: 0.1 Date: 21-Sep-2018 Prepared By: Mithi Prasad, Sarang Kulkarni, Manish Gupta Checked By: Yogesh Jadhav Approved By: Satish Kumar P Page: 322 of 1052 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. P0686 - 94: Main relay command (unexpected operation) – Unexpected Operation DTC Description as per ISO standard Main relay command – Unexpected operation ECU Pin Number K88,K01,K03,K05 (supply after main relay) Customer Symptom MIL ON Fault Effects (On Vehicle) Vehicle may not start Lamp Status (If Any) MIL ON1 (Lamp turn On immediately when fault detected) Fault Detection Condition (Root cause) Ignition ON Normal Operating Condition Fault condition no more present Probable Trouble Area 1. Check the other DTCs 2. Main relay circuit open intermittently 3. EMS ECU. Healing Condition 1. Run the diagnostic procedures to check the ECU Power & ground. 2. Check Supply after main relay 3. Clear the DTC. 4. Read the DTC once again. Component Details: EMS ECU is an electronic controller which controls the Engine functionality by interfacing with various sensors, actuators And other controllers (via CAN). Preliminary Checks: 1. Check whether the customer voice / view about the issue is matching with the fault effects mentioned above. 2. If yes, go ahead with next steps. If not, check for other DTC’s presence. 3. Check whether similar complaints are earlier reported. If yes, perform the preliminary checks with respect to 4. Earlier issue closure. Check for pin back out at EMS ecu connector. 5. Check whether the EMS is receiving Battery supply and Ground 6. Check whether the Battery is healthy.
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