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OSPREY- Application
DTC Troubleshooting Data
Version: 4.0
Date: 10-02-2017
Prepared by: Mithipati Prasad
Checked by: G S Raju / Senthilnathan S
Page: 476 of 654
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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.
P0685: ECM/PCM Power relay Control Circuit/Open - Relay Stuck Open
Overview:
DTC Description as per ISO standard
ECM/PCM Power Relay Control Circuit/Open
ECU Pin Number
12, 31
Customer Symptom
Engine will not start
Fault Effects (On Vehicle)
Cannot communicate with the ECU.
Lamp Status (If Any)
-
Fault Detection Condition
This DTC gets logged due to EMS power supply cutoff due to drop out of
main power relay..
Normal Operating Condition
Diagnostic tool displays the Battery supply status at ignition ON.
Probable Trouble Area
ECU Main relay, ECU, Wiring harness
Healing Condition
Clear the errors, Ignition OFF to ON, engine idle & fly-up condition
Component Details:
EMS ecu gets wake up with Ignition switch input and energizes the main power relay coil to get the power supply to EMS.
Preliminary Checks
x
Check whether the customer voice / view about the issue is matching with the fault effects mentioned above. If
y
es, go ahead with next steps. If not, check for other DTC’s presence.
x
Check whether similar complaints are earlier reported. If yes, perform the preliminary checks with respect to
earlier issue closure.
x
Check whether the EMS ECU is getting power supply and GND. Rectify wiring Harness as per the schematic if
found faulty.
x
Check whether the Fuse of EMS main relay supply is blown Off. If so replace the fuse.
x
Check whether the Main relay is faulty / contacts stuck open. Rectify/Replace if found main relay is faulty.
x
Check for damage / back out of pins at EMS Connector. If found rectify / replace.