Fuel System Monitoring

GENERAL DESCRIPTION

The fuel system monitoring includes the lambda controller restriction against the limits for rich and lean and the permanent deviation from the mean position.

MONITORING STRUCTURE

If the fuel system is suddenly hard disturbed (e.g. by a leaky injection valve) and therefore the lambda controller reaches the restriction (lean limit) a timer is started. The timer is incremented as long as the controller remains at the limit. If the timer exceeds a predetermined value a fault for short trim will be detected and stored.

For permanent deviation from the mean position there are additional lean and rich thresholds. If the accumulated time (sum of all excesses for rich and lean) is greater than a fixed limit during a defined period a fault for long term trim will be detected and stored.

MONITORING CONDITIONS





- closed loop conditions
- evap purge amount < below a defined percentage of lambda deviation

threshold exceedance = T1 + T2 + T3 + T4 + T5

Lmax. = restriction for rich limit
Lmin. = restriction for lean limit
TLmax. = threshold for rich exceedance
TLmin. = threshold for lean exceedance