Description

Fuel System Monitoring Description

Primary Mixture Control
The air mass taken in by the engine and the engine speed are measured. These signals are used to calculate an injection signal. This primary mixture control follows fast load and speed changes.

Lambda-control






The ECM compares the oxygen sensor signal upstream of the catalyst with a reference value and calculates a correction factor for the primary control.

Adaptive Control






Drifts and faults in the sensors and actuators of the fuel delivery system, as well as un-metered air leakage into the intake system influence the primary control. This causes deviations in the air to fuel ratio. The adaptive control determines the controller correction in two different ranges.

Range 1 - Additive Correction per time unit
Lambda deviations in range 1 are compensated by an additive correction value multiplied by an engine speed term. By this means an additive correction per time unit is derived.
Range 2 - Multiplicative Correction
Lambda deviations in range 2 are compensated by a multiplicative factor.
Each value is determined only within its corresponding range. But each adaptive value corrects the primary control within the whole load and speed range of the engine. After the next start, the stored adaptive values are included in the calculation of the primary fuel control; just before closed-loop fuelling control is activated.

Abbreviations for the Fuel Delivery System:
QU1 upper airflow threshold range 1
NU1 upper engine speed threshold range 1
tra additive learning correction coefficient per time unit (range 1)
TRADN lower diagnosis threshold of tra
TRADX upper diagnosis threshold of tra
TLARN upper engine load threshold f(n), range 2
QL2 lower airflow threshold range 2
TLL2 lower engine load threshold range 2
fra multiplicative learning correction coefficient (range 2)
FRADN lower diagnosis threshold of fra
FRADX upper diagnosis threshold of fra

Diagnosis of Fuel Delivery System
Faults in the fuel delivery system can occur which cannot be compensated for by the adaptive control. In this case the adaptive values leave a predetermined range. If the adaptive value is outside this predetermined range, and then if the condition is again present on a subsequent drive cycle, the MIL is illuminated and the appropriate diagnostic trouble codes are stored.