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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: 940 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.
P1275-4B: Over Temperature of the power stage for AC compressor – Over Temperature of the power stage for
AC compressor
Overview:
DTC Description (User Friendly)
Over Temperature of the power stage for AC compressor
ECU Pin Number
K090
Customer Symptom
MIL OFF, CEL ON. Vehicle cabin will not be cooled even after
AC is turned ON.
Fault Effects (On Vehicle)
AC Will not work (Cabin Cooling will not happen).
Lamp Status (If Any)
CEL ON. CEL Turns Off as and when fault condition is not
present / healed.
Fault Detection Condition (Root cause)
The hardware detects an over temperature error on the digital
output power stage for the actuator (K090).
Normal Operating Condition
No Fault
Probable Trouble Area
Check, whether there is dis-continuity in wiring harness
between AC Relay and EMS ECU.
Check for ECM pin K090 is SC to Battery
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 for any mechanical damage in AC Relay
Replace faulty Relay Go to next step
2
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.