1.6.5 Diagnosis of Fuel System - summary error

P2177/P2179 (FMASmax/FMAS2max), P2178/P2180 (FMASmin/FMAS2min), P2187/P2189 (FMASsig/FMAS2sig), P2188/P2190 (FMASnpl/FMAS2npl). 

This function is part of the diagnosis of the fuel system. It is just an administrative function to aggregate and summarize the detailed failures detected by the fuel system diagnosis to a general failure path FMAS. This is done to guarantee MIL illumination after 2 driving cycles.

It is demanded that any fuel system fault detected in a driving cycle is confirmed by any other fuel system fault in the next driving cycle. This means e.g. that if an additive fuel system fault (RKAT) was detected in the last driving cycle and a multiplicative fuel system fault (FRAO, FRAU) is detected in the current driving cycle, the MIL must be illuminated. This is ensured by introducing and using the general summary failure path FMAS for MIL illumination.

The relation between the detailed failure path of the fuel system diagnosis (RKAT, FRAO, FRAU) and the corresponding summary failure path FMAS is shown in the flowchart.

A description of the detailed failure paths RKAT, FRAO and FRAU can be found in the document "Diagnosis of fuel system".

This function is able to analyze the detailed failure paths of up to 2 banks, each bank with its own summary failure path. The handling of the detailed failure paths of each bank is done separately but all in the same way.