Functions of Bus System Analysis
Bus system analysis is a test module that automatically executes the following steps:
Step 1: Identification of engine type
Identifying the engine type is a prerequisite for bus system analysis, since: different engines generate different fault code memory entries for the same cause of fault.
Step 2: Read fault memories of all control units
Step 3: Check fault memory entries for undervoltage
If the vehicle has suffered an undervoltage, the undervoltage is the most likely cause of the bus failure. Bus system analysis checks whether a fault memory entry indicating undervoltage is present in at least 2 control units.
If no undervoltage can be detected, continue with step 4.
Step 4: Check how many fault memory entries were found
If at least 1 fault memory entry is present, continue with step 5.
Step 5: Evaluation of fault memory entries and creation of a list of most probable fault causes
Bus system analysis computes the 3 most probable fault causes.
The 3 most probable fault causes are given in a list.
The most probable fault cause is at the top of the list.
The number of stars denotes priority.
The stars in front of a cause of fault indicate how probable the cause of fault is. 5 stars denote the most likely cause of fault.
1 star is allocated to a cause of fault that has very low probability.
Step 6: Selection of the test module
The BMW diagnosis system proposes a separate test plan for each of the 3 most probable fault causes.