Generating diagnostic trouble codes: Notes

WARNING: This page is about a different car, the 2003 Saab 9-3. However, it is still accessible from the selected car via links, so may be relevant.

Fuel Level, plausibility diagnosis: Because the fuel level is used as enable criteria in certain diagnoses, the control module must know that the fuel level value is plausible. The way it works is that the Trionic receives a bus message "Fuel level XX litres" from the MIU. During driving the Trionic observes the value and as the car is driven, fuel is consumed. The Trionic makes sure the fuel level value drops. In the Trionic a number of important filtrations are carried out to avoid faults caused by, for instance, splashing fuel in the tank, starting uphill. The fuel level diagnosis can be called a support diagnosis as it does not generate a DTC, but if for instance the EVAP Purge valve diagnosis has reported a leakage in the EVAP canister purge valve then DTC P0441 is normally generated. If on the other hand the tank integrity diagnosis has reported the same fault and the fuel level diagnosis has simultaneously reported a fault then DTC P1441 is generated instead.
DTC P0441 and P1441 are generated when fault criteria have been fulfilled during Test 1 or Test 2 and the dependents are OK.