Air Injection: Testing and Inspection

Secondary Air Diagnosis With Two-Step Lambda Control







Principle
The Check of the Secondary Air System is performed in an idle period. The air pump is switched on especially to run the check.

Evaluation during secondary air injection (=SAI):
Calculation of nominal secondary air mass is dependent on battery voltage, ambient density, and exhaust pressure.

Calculation of nominal lambda(exhaust) dependent on secondary air dilution factor and required engine enrichment lambda(engine):







Two-step lambda control dependent on the actual lambda(exhaust) signal from the lambda sensor.

Calculation of M SAI, actual from two-step lambda control (fr = lambda correction factor):







Evaluation after deactivation of SAI
Check of pilot control and reject result, if threshold is exceeded.

Fault evaluation
Fault detection after comparison of the quotient of secondary air mass flow to fault threshold.
(fr: multiplicative factor - closed loop regulator)


Secondary Air Diagnosis with Two-Step Lambda Control - Diagnosis During Active SAI (Flow Cart must be changed . Please Consult, Stephan)