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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