1.6.1.1 Monitoring Function

Two separate monitors are utilized for the fuel system diagnosis. The first monitor evaluates the percentage of the long-term fuel adaptation, and the second monitor evaluates the percentage of the short-term fuel trim physical limits.

The short-term fuel trim is monitored in every engine state except for DFCO and the long-term fuel trim is evaluated while it is in its learning process. The latter diagnosis is inactive during the EVAP System canister purge phases. Therefore, an additional learning process can be initiated if large deviations in the short-term fuel trim occur and the monitor can be executed. When the enable conditions are fulfilled, different counters are started for both evaluations. When no condition is fulfilled, the end diagnostic counter will decrement from a calibratable value to zero and a passing decision is made.

When a lean condition is present and total fuel control exceeds the calibratable threshold, two timers are started. When the lean threshold counter exceeds the calibratable threshold before the reset timer has decremented from the calibratable threshold to zero, a lean error is set.

When a rich condition is present and total fuel control remains below the calibratable threshold, two timers are started. When the rich threshold counter exceeds the calibratable threshold before the reset timer has decremented from a calibratable threshold to zero, a rich error is set.

The time counters are increased while the "lambda controller" or the "lambda adaptation" exceeds its respective minimum or maximum thresholds.

The error is detected as soon as one of the time counters achieves its maximum value.