284 / 1980
278
ENGINE 273 MPFI
ISO/SAE controlled codes (core DTCs)
ISO/SAE-controlled diagnostic trouble codes are those
codes where industry uniformity has been achieved.
These codes were felt to be common enough across
most manufacturers’ applications that a common
number and fault message could be assigned.Although
service procedures may differ widely amongst
manufacturers, the fault being indicated is common
enough to be assigned a particular fault code.
TATAMotors controlled codes (nonuniformDTCs)
Areas within each alpha designator have been made
available for TATAMotors-controlled DTCs. These are
fault codes that will not generally be used by TATA
due to basic system differences, implementation
differences, or diagnostic strategy differences. When
TATA designs and specifies diagnostic algorithms,
software and diagnostic trouble codes are strongly
encouraged to remain consistent across their product
line when assigning codes in the manufacturer-
controlled area. For power train codes, where possible,
the same groupings should be used as in the ISO/
SAE controlled area, i.e. 100’s and 200’s for fuel and
air metering, 300’s for ignition system or misfire etc.
all DTC words meets ISO 15031-2.
MIL INDICATOR
Malfunction Indicator Lamp (MIL) is located in the
instrument panel and it indicates the presence of any
malfunction/fault in the system/vehicle to the
customer.
On ignition ‘ON’ the MIL comes ON and after engine
starting it goes OFF. In case of any memorized
malfunction/fault in the EMS, the lamp remains ON
alerting the presence of the abnormality to the user.
The MIL remains ON as long as the fault is active
unless until either the fault is ‘erased’ or it has been
rectified.
MIL & DTC Management
Software systems are present in the engine control
system (ECU) to check correct performance of
Sensors and actuators, and also to check electrical
circuit continuity. Open or short circuits can be
detected quickly, whereas correct performance checks
by the system's internal monitors are only made when
the engine is in stable conditions for which calibrations
are available – for example, cruising at steady speed.
The software monitors run under defined conditions
and can signify that they have run correctly. If the
necessary conditions are not met or are not met for
long enough in a trip then the monitors will not run to
completeness.
If a particular monitor ran successfully during a trip
after a fault had been detected on an earlier trip but
found no fault then the Diagnostic system could use
the information as part of a self-heal process to
recognize a disappeared MIL-active fault en route to
MIL deactivation.
CKNL Activation Strategy
The CKNL is illuminated to alert the driver after a
calibration delay when the valid fault is detected in the
system. For some faults this calibration delay is one
driving cycle (ignition ON-OFF cycle) and for some it
is more than one driving cycle, depending on priority.
E.g. for crank shaft sensor and misfire faults the MIL
illuminates in the first driving cycle itself. (For misfire
detection, vehicle has to run for some time in normal
conditions) For lambda sensor and TMAP sensor faults
the MIL illuminates after 3 driving cycles.
MIL Extinguishing
The MIL is extinguished on the third drive cycle after a
detected MIL-active fault is no longer detected. But
the related information (like P codes) will still retained
in the memory (as a fugitive) till 40 drive cycles after
whichwill be erased automatically. It will give information
about the history of the faults. In case of an ‘erasing’
action done via a diagnostic tool, no information will
be retained in the ECU memory.
Non monitoring (Inactivation) Zone
Monitoring above 2500 m (TBC) altitude and below
ambient temperature of –7°C (TBC) is unreliable
because of driving pattern differences to the target
regions, lying above that temperature. The misfire
monitoring strategy is disabled when the fuel level in
the tank is below 20% due to the possibility of the air
getting in the system and engine rpm above 5400 rpm.
Therefore, the diagnostic system is disabled under
this condition.
Methods of Diagnostic
There are two ways we can diagnose the problems in
EMS.
1) On Board Diagnosis or Laptop based Diagnosis
2) Blink Code (Crude Method) based on Short-Link