On Board Diagnostics

Powertrain Control Module (PCM) performs the pursuing functions in relation to:

OBD II Diagnostics:

Carry out micro-processor based self diagnostics to be certain accurate procedure of the PCM and secure storage of OBD II diagnostic facts in memory.

Perform On-Board diagnostics in genuine time and inform the driver by illuminating MIL in case of a fault conduct powertrain regulate features to reduce emissions and meet OBD II rules throughout open up-loop operation at start out-up time.

Conduct powertrain handle features to cut down emissions and fulfill OBD II regulations in closed-loop regulate in the course of regular procedure.

Execute microprocessor-dependent self diagnostics to make certain appropriate operation of the PCM and harmless storage of OBD II diagnostic info in memory.
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The PCM performs the next self diagnostics:

· Confirm the checksum of the method memory in ROM with its perform and suitable version.

· Execute go through and produce test of RAM cells for fault totally free memory Complete processor features in CPU, peripheral products which includes A/D converters, watchdog timers, and registers to validate that the processor is performing properly.

· Conduct checks on stored vehicle knowledge and confirm that the details is not corrupted and is in fair limitations of car procedure.

· Complete On-Board diagnostics in true time and alert the driver by illuminating MIL in situation of a fault, by interspersing diagnostics with car or truck management functions.

The diagnostics are categorised into priority ranges from one to eight or 9. The highest priority degree checks are completed just about every 1 millisecond, followed by upcoming precedence amount assessments every single 5 milliseconds, 10 milliseconds, 20 milliseconds, fifty milliseconds, a hundred milliseconds, two hundred milliseconds, 500 milliseconds, and 1 2nd. The optimum precedence stage checks are those that outcome basic safety and emissions to a higher degree according to OBD II restrictions. These consist of Oxygen sensor (lambda sensor), and gasoline trim checks in the course of shut loop operation of the automobile. The next priority checks are the interrupt timers, and watchdog timers. The following precedence assessments are sensors, together with Ego sensor, Throttle placement sensor, Misfire detection, MAP sensor, Motor RPM sensor, MAF sensor, Crankshaft situation sensor, and Motor coolant sensor. The up coming priority exams are EGR intrusive exams, Catalytic converter’s secondary air, and canister purge, fuel stage sensor, pedal actuator, and ignition timer. The following precedence checks are periodic self tests.

The PCM performs on-board diagnostics in authentic time The PCM is interrupted by the genuine time scheduler during the performance of its typical vehicle management features when the on-board assessments are owing. At this time the PCM saves its present-day state of the car or truck and performs the diagnostics. This usually takes about one hundred microseconds. Then the PCM returns to its normal motor vehicle management capabilities. This repeats for just about every precedence amount diagnostics. In this method the PCM spends about 15-40% of its time to diagnostics and the rest to perform its standard auto manage functions.

The technique of testing each and every component relies upon on the electrical attributes and automobile functions performed by the machine. The PCM maintains the very low and superior boundaries for each and every test parameter, and typical assortment of values and performance demands for just about every element that it exams. The PCM also has adequate components test ability to come across a shorter circuit, or open up circuit, or the noise degree of a signal, like battery, electrical power provide, wiring harness, each individual sensor, actuator and manage unit relevant to emissions regulate.

The PCM tests just about every sensor by measuring each and every take a look at parameter, these types of as input, or output and comparing it with the anticipated price stored in the technological details for the sensor.

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