Generation of DTCs

Fuel level, Plausibility diagnosis: Because fuel level is used as an enable criteria in certain diagnosis, then the control module must know that fuel level value is plausible. It works in such a way that ECM receives the bus message "Fuel level XX liter" from MIU. While driving ECM observes the value and as the vehicle is driving it is consuming gasoline, ECM sees that the fuel level value will fall. In ECM there is a number of filtrations of the value so as to avoid inaccuracies due to for example splashing fuel in the tank and hill starts. The fuel level diagnosis can be said to be a support diagnosis, it does not generate its own DTCs, but if for example the tank pressure sensor diagnosis has reported a performance problem in the tank pressure sensor then DTC P1451 is normally generated. If on the other hand the tank pressure sensor diagnosis has reported the same fault and the fuel level diagnosis at the same time has also reported a fault then DTC P1491 is generated instead.

DTCs are generated if the fault criteria are fulfilled and the dependents are OK.