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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: 885 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.
P0646-11: A/C Clutch Relay Control Circuit Low – AC compressor (Short circuit to ground)
Overview:
DTC Description (User Friendly)
AC compressor (Short circuit to ground)
ECU Pin Number
K090
Customer Symptom
MIL OFF, CEL ON. Low Fuel efficiency
Fault Effects (On Vehicle)
AC Compressor will remain engaged as when Engine starts
running (irrespective of AC Request).
Lamp Status (If Any)
CEL ON. CEL Turns Off as and when fault condition is not
present / healed.
Fault Detection Condition (Root cause)
ECM pin K090 is shorted to Ground
Normal Operating Condition
No Fault
Probable Trouble Area
Wiring Harness connections between AC Relay and EMS
ECU.
AC Relay faulty,
EMS ECU faulty
Healing Condition
Rectify the error
Clear through diagnostic tool
Ignition OFF & ON
Component Details:
AC Compressor has a magnetic Clutch; EMS ECU energizes Coil of the magnetic clutch. After
being energized, Clutch engages the compressor to the EMS ECU.
Preliminary Checks:
1. Check whether the customer voice / view about the issue is matching with the fault effects mentioned in above
Table. If yes, go ahead with next steps. If not, check for other DTC’s presence.
2. Check whether other customers report similar complaints earlier. If yes, perform the preliminary checks with
respect to earlier issue closure.\
3. Check, whether the AC is functional, if AC is not functional, then check the wiring harness connections between
EMS ECU and AC Relay.
4. Loose/ Damaged Connections between AC Compressor Relay and EMS ECU.
5. Loose/ Damaged Connections between AC Compressor Relay and Battery supply or Ground.
6. Check for proper installation of AC relay in fuse box.
7. Check for damage of pins at ECU connector.
Trouble Shooting:
Step Checks
IF YES
IF NO
1
Check Whether the AC Compressor Relay is installed on
Vehicle
Go to Next Step
Fit AC Compressor
Relay
2
Check for any mechanical damage in AC Relay
Replace faulty Relay Go to next step
3
Is there wiring harness electrical continuity between ECU
pin 48 & AC relay pin
3
. Also Check continuity between the
Main Relay supply and the AC relay pin
1
. Also check
continuity from AC Relay pin
1
to GND.
Go to next step
Rectify the wiring
harness
connections as per
the circuit
schematic.