Overview
This document contains information on:
General
Function requirements
Function
General
A constant, stoichiometric fuel ratio with (λ < 1) is required for efficient operation of the catalytic converter. The catalytic converter monitoring ensures that the hydrocarbon emissions (HC) do not exceed the legally prescribed limit value. This means the aging of the catalytic converter is monitored.
Function requirements
Operating temperature of catalytic converters reached
Lambda control active
Fuel ratio (λ < 1)
Function
The aging of the catalytic converter is caused by the reduction of the oxygen storage capacity over time and the resulting decrease in hydrocarbon conversion. To check the oxygen storage capacity, the following measurements take place:
A rich mixture (λ < 1) is available. The time is measured that it takes until the lambda sensor downstream of the catalytic converter has reached a defined maximum value and the largest portion of the oxygen has depleted.
A lean mixture (λ > 1) is available. The time is measured that it takes until the lambda sensor downstream of the catalytic converter has reached a defined minimum value and the catalytic converter has filled up its oxygen store.
If the time measured lies below a stored characteristic, then the oxygen storage capacity is inadequate and the combustion engine control unit notes a fault in the fault memory.