NEXON DIAGNOSTIC MANUAL

OSPREY- Application

DTC Troubleshooting Data

Version: 4.0

Date: 10-02-2017

Prepared by: Mithipati Prasad

Checked by: G S Raju / Senthilnathan S

Page: 312 of 654

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: ECM/PCM Power relay Control Circuit Low - Relay Stuck

Overview:

DTC Description as per ISO standard

ECM/PCM Power Relay Control Circuit Low

ECU Pin Number

12, 31, 41, 49

Customer Symptom

Battery will gets drained in very less time.

Engine will not start

Fault Effects (On Vehicle)

EMS ecu will not be turned Off even after Ignition switch is turned Off.

EMS ecu will not get power

Lamp Status (If Any)

Fault Detection Condition

This DTC gets logged if the ECU main power supply relay gets stuck.

If stuck closed then EMS ecu will get power supply continuously, if

stuck open then EMS ecu will not get power supply.

Normal Operating Condition

Diagnostic tool display the Battery supply status at ignition ON

Probable Trouble Area

ECU Main relay, ECU, Wiring harness

Component Details:

EMS ecu gets the wake up input through the Ignition switch input. EMS ecu gets the power supply through the Main /

Power Hold relay. EMS ecu turns the Main relay ON as soon as its Ignition switch input is Active.

Preliminary Checks

Check whether the customer voice / view about the issue is matching with the fault effects mentioned above. If

yes, go ahe

ad with next steps. If not, check for other DTC’s presence.

Check whether similar complaints are earlier reported. If yes, perform the preliminary checks with respect to

earlier issue closure.

Check whether the EMS ECU is getting power supply and GND. Rectify wiring Harness as per the schematic if

found faulty

Check whether the Main relay is faulty. Rectify/Replace if found main relay is faulty.

If fault still persists then Call Hot Line