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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: 296 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.
P0646: Air conditioning relay control – circuit short to ground
Overview:
DTC Description as per ISO standard
AC Clutch Relay Control Circuit Low
ECU Pin Number
48
Customer Symptom
AC Compressor will be continuously engaged irrespective of
AC Request which will reduce the fuel efficiency.
Fault Effects (On Vehicle)
AC Compressor will be continuously engaged.
Lamp Status (If Any)
CE lamp is on
Fault Detection Condition
This fault gets logged if the AC Clutch control pin of EMS ECU
is short circuited to ground.
Normal Operating Condition
Healthy wiring harness connections between AC Relay and
EMS ECU
Probable Trouble Area
AC Clutch relay
Related wiring Harness, connector or terminals
ECU
Component Details:
AC Compressor has a magnetic Clutch; Coil of the magnetic clutch is energized by EMS ECU. After getting Energized,
Clutch engages the compressor to the EMS ECU.
Preliminary Checks:
x
Check whether the customer voice / view about the issue is matching with the fault effects mentioned above. If
yes, 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
Loose/ Damaged Connections between AC Compressor Relay and EMS ECU.
x
Loose/ Damaged Connections between AC Compressor Relay and Battery supply or Ground.
x
Check for proper installation of AC relay in fuse box.
x
Check for damage of pins at ECU connector.