Method for detecting malfunctions in a motor vehicle

Method for determining causes of malfunctions in a motor vehicle having a plurality of subassemblies and means for communicating data words generated in said subassemblies to an analysis unit, said data words containing information concerning said malfunctions of said motor vehicle, said method comprising the steps of:

• generating respective first data words in each subassembly in which a malfunction is detected;
• generating respective second data words in each subassembly which is peripheral to a subassembly in which a malfunction is detected;
• communicating said first and second data words to said analysis unit;
• generating a functional chain in said analysis unit in response to said first and second data words, said functional chain comprising potential causes of said detected malfunctions;
• generating a list of test steps in said analysis unit, said list comprising test steps to check said potential causes of said malfunctions, including potential causes of malfunctions which cannot be detected automatically by a subassembly and for which no data word is therefore formed;
• storing said list of test steps;
• executing said test steps;
• checking said functional chain and locating causes of said malfunctions in said subassemblies;
• generating and displaying remedial measures corresponding to said causes of said malfunctions;
• and
• optimizing a sequence of test steps in said list of test steps
• by eliminating redundant test steps in said list which occur due to listing of particular potential causes of malfunction more than a single time, whereby each test step is performed only once;
• and
• by executing first those test steps which relate to potential causes of malfunction for which probability of a malfunction is higher than for other potential causes of malfunction, and those which relate to a potential cause of malfunction which must be checked before further potential causes of malfunction can be checked.