Monitoring Function
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At the beginning of the rationality check the fuel consumption is reset and the actual fuel level is stored. Then the fuel consumption is continuously summed up, until the diagnostic volume is reached. Then the difference between stored and actual fuel level is calculated and compared with the diagnostic volume. If the deviation is too large, a fault code is stored.
If refueling is detected, the rationality is reset.
If the fuel level sensors signs almost or complete full tank, no refueling can be detected with the sensors. So the fuel consumption is reset, if ignition is switched off because refueling is possible. If the consumption exceeds a threshold, and the fuel level sensors signs still almost full, a fault code "stuck full" is stored.