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Home >> Jaguar >> 2019 >> XF S >> Repair and Diagnosis >> External Pages >> Different car >> Section 200 (Electronic Engine Controls - V8 S/C 5.0L Petrol, Project 8 -- XE/(760)) >> Electronic Engine Controls - V8 S/C 5.0L Petrol, Project 8 (G2261903) >> Description And Operation >> Electronic Engine Controls >> Operation >> Misfire Detection

Misfire Detection

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Legislation requires that the Powertrain Control Module (PCM) must be able to detect the presence of an engine misfire. It must be able to detect misfires at 2 separate levels. The first level is an amount of misfire that could lead to the legislated emissions limit being exceeded by a given amount. The second level is a misfire rate that causes degradation in catalytic converter efficiency.

The PCM monitors the number of misfire occurrences within 2 engine revolution ranges. If the PCM determines a misfire failure within either of these 2 ranges, over 2 consecutive journeys, it will record a fault code and details of the engine speed, engine load and engine coolant temperature. In addition, if the second level of misfire occurs, on any trip, the PCM flashes the Malfunction Indicator Lamp (MIL) in the Instrument Cluster (IC) while the fault is occurring.

The signal from the Crankshaft Position (CKP) sensor indicates how fast the poles on the drive plate are passing the sensor tip. A sine wave is generated each time a pole passes the sensor tip. The PCM can detect variations in drive plate speed by monitoring the sine wave signal supplied by the crankshaft position sensor. By assessing this signal, the PCM can detect the presence of an engine misfire. The PCM will evaluate the signal against a number of factors and will decide whether to record the occurrence or ignore it. The PCM can assign a misfire judgment to an individual cylinder, which can be viewed on Jaguar Land Rover (JLR) approved diagnostic equipment.

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