Test Group WBMXV01.9M44
General Description - Air mass taken in by the engine and the engine speed are measured. These signals are used to calculate an injection signal. This mixture pilot control follows fast load and speed changes. ECM controller compares oxygen sensor signal of sensor upstream of catalyst with a reference value and calculates a correction factor for pilot control. See Fig 1.
Adaptive Pilot Control - Drifts and faults in sensors and actuators of fuel delivery system as well as not measured air leakage influence pilot control. This causes increasing deviations of air/fuel ratio. Adaptive pilot control effects controller correction in 3 different ranges. Lambda deviations in range one are compensated by an additive correction value multiplied by an engine speed term. By this an additive correction per time unit is created. Lambda deviations in range 2 are compensated by a multiplication factor. Lambda deviations in range 3 are compensated by an additive correction per injection. A combination of all 3 ranges will be correctly separated and compensated. Each value is adapted in its corresponding range only. But each adaptive value corrects pilot control within whole load/speed range. At next start, stored adaptive values are included in calculation of pilot control just before closed loop control becomes active. See Fig 2.
Diagnosis Of Fuel Delivery System - Faults in fuel delivery system can occur which cannot be compensated for by adaptive pilot control. In this case, adaptive values leave a predetermined range. If adaptive value is outside a plausible range, then MIL is illuminated and fault is stored. See Fig 3.