2002 2BMXV03.2S54 & 2BMXV04.9S62
WARNING: This page does not describe the selected car, but rather 18 other vehicles, including the 2002 BMW Z8, 2002 BMW Z3, 2002 BMW X5, 2002 BMW M5, and 2002 BMW M3. However, it is still accessible from the selected car via links, so may be relevant.
- General Description
- Measure Principle - Method of engine misfire detection is based on monitoring crankshaft acceleration. Engine roughness is derived from differences from segment periods (90 degree crank angle) duration which are corrected and compared to a load and engine-speed dependent thresholds. Different statistical methods are used to distinguish between normal changes of segment duration and changes due to misfire. See Fig 1. Segment periods are measured through an angular range of 90 degree crank angle. The segment starts 54 degrees before TDC. Beginning and end of the segments are located at the same angle. Duration of crankshaft segments is measured continuously.
- Sensor Wheel Adaptation - To eliminate manufacturing tolerances and off-center installation, adaptation of sensor wheel tolerances is carried out during fuel cut-off. Segment periods are corrected by adaptation values. With progressing adaptation, sensitivity of misfire detection is increasing.
- Calculation Of Engine Roughness Threshold Value - Engine roughness threshold value consists of base value, which is determined by a load/speed dependent map. During warm-up, base value is multiplied by a coolant temperature dependent correction value. Without sufficient sensor wheel adaptation, engine roughness threshold is limited depending on wheel tolerances expected.
- Misfire Monitoring Structure - See Figure.
- Fault Processing -
See Fig 2.
- Error Window - Within an interval of 200-1000 crankshaft revolutions, "error windows" to check for similar engine conditions are determined. Upon detection of misfire, window is extended if current operating point is not within window.
- Engine Operating Point Window - Engine operating window is updated with each segment without misfire.
- Misfire Detection (Emission Increase) - Within an interval of 1000 crankshaft revolutions (4000 segments), detected misfire events are added for each cylinder. If sum of all cylinder misfire incidents exceed a predetermined value, a fault code is stored. If more than one cylinder is misfiring, all misfiring cylinders will be specified and individual fault codes for all misfiring cylinders and for multiple cylinder will be stored.
- Misfire Detection (Catalyst Damage) -
Within an interval of 200 crankshaft revolutions, detected number of misfiring events is weighted and calculated for each cylinder. Weighting factor is determined by a load/speed dependent map. If sum of cylinder misfire incidents exceeds a predetermined value, a fault code is stored and MIL is illuminated. If cylinder selective count exceeds predetermined threshold, following measures take place:
- Lambda closed loop system is switched to open-loop.
- Cylinder selective fault code is stored.
- If more than one cylinder is misfiring, fault codes for all individual cylinders and for multiple cylinders will be stored.
- Fuel supply to respective cylinder is cut-off.