Safety system: time-out error

The BYTEFLIGHT bus system has a star-shaped structure. The individual satellites (= control modules with/without sensors) are interconnected across a star connector by means of fiber-optic cables. The star connector in the BYTEFLIGHT bus system is the Safety and Information Module. There is a transmission and a reception module (transmitter and receiver) as a unit in each satellite for connecting to the BYTEFLIGHT bus. The unit has an integrated transmit and receive diode.

Main functions

Fault memory entry: Message (identifier) from control module x missing

According to a fixed and known pattern, a certain message (e.g. A) is transmitted in cycles from a transmitting control module. The receiving control modules that expect this message in cycles can determine whether this message is missing or arrives too late. If this fault is detected, the above fault memory entry is made in a receiving control module.

The table below shows which messages are sent and/or received by which control module. The first vertical column contains the transmitting control modules (TCU); the first horizontal line contains the receiving control modules (RCU ). A transmitting control module can transmit various messages to the receiving control modules. A certain message is indicated by the identifier in brackets below the transmitting control module. This table can be used to determine which receiving control modules would have to generate a fault memory entry if a message from the transmitting control module fails. If, for example, the SIM is no longer transmitting message A, the fault memory entry ”Message (A) from Safety and Information Module missing” is created in the STVL (front left door satellite) and STVR (front right door satellite).

If a ”Message (identifier) from control module x missing” fault is entered in a receiving control module, then a message from a transmitting control module has failed. In order to locate the cause of the fault, it must first be determined whether this fault is also entered in other receiving control modules. In this way, the cause of the fault can be located. In this context, three cases are distinguished:

• Assumption: a message is received by several control modules and the ”Message (identifier) from control module x missing” fault is stored in only one receiving control module. There are then the following possible faults:
  
  • Receiving control module or
    
  • Safety and Information Module or
    
  • Fiber-optic cable between receiving control module and Safety and Information Module or
    
  • Plug-in connections to the two control modules (connector not properly engaged, loose contact, etc.)
    
• Assumption: a message is received by several control modules and the ”Message (identifier) from control module x missing” fault is stored in all receiving control modules. There are then the following possible faults:
  
  • Transmitting control module or
    
  • Safety and Information Module or
    
  • Fiber-optic cable between transmitting control module and Safety and Information Module or
    
  • Plug-in connections to the two control modules (connector not properly engaged, loose contact, etc.)
    
• Assumption: a message is received by several control modules and the ”Message (identifier) from control module x missing” fault is stored in a number of receiving control modules (not all!). Then a general statement is no longer possible. The defect might then lie at the connector of the Safety and Information Module.
  In order to precisely identify whether the control module or fiber-optic cable is defective, the BYTEFLIGHT bus must be tested optically! The test programs for the optical test on the BYTEFLIGHT bus can be found under function selection: Body, Bus Functions, BYTEFLIGHT Functions and Optical Test.
  

Procedure in the case of fault memory entry: ”Message (identifier) from control module x missing”

Assuming that the ”Message (1) from STVL missing” fault is stored in one control module (e.g. SSBF), Use the following procedure:

• Look for the row in the Table that contains the transmitting control module (TCU) STVL with message (1).
  
• From the Table, establish which control modules are receiving this message. For the above example, these are the control modules SBSR, SIM, SSBF and SSFA.
  
• Display the fault memory list of the control modules SBSR, SIM, SSBF and SSFA from the short test and fault-pattern selection (other option: switch to ”Control-module functions” of these control modules and read the fault memory)
  

• If the ”Message (1) from STVL missing” fault is entered in all receiving control modules SBSR, SIM, SSBF and SSFA, then there are the following possible faults:
  
  • Transmitting control module STVL
    
  • Safety and information module
    
  • Fiber-optic cable between STVL and Safety and Information Module
    
  • Plug-in connections at the two control modules
    
• If the ”Message (1) from STVL missing” fault is only entered in one receiving control module, e.g. SSBF, then there are the following possible faults:
  
  • Receiving control module SSBF
    
  • Safety and information module
    
  • Fiber-optic cable between SSBF and Safety and Information Module
    
  • Plug-in connections at the two control modules
    
• In order to precisely identify whether the control module or fiber-optic cable is defective, the BYTEFLIGHT bus must be tested optically. The test programs for the optical test on the BYTEFLIGHT bus can be found under function selection: Body, Bus Functions, BYTEFLIGHT Functions and Optical Test.
  

Fault memory

The following additional information regarding the individual fault memory entries can be obtained:

• Fault occurred at t > 1 min (i.e. a time greater than 1 minute)
  
• Fault occurred at 1 s < t < 1 min (i.e. a time between 1 second and one minute)
  
• Fault occurred at 0 s < t < 1 s (i.e. a time between 0 and 1 second)
  
• Fault start system time, e.g. 5.34 h
  
• Fault end system time, e.g. 5.38 h
  

The first three additional items of information can also occur as a combination. In the BYTEFLIGHT system, there is a uniform system time for all participants (slaves). On production of the vehicle, the system time is started by means of a diagnosis command. In the above example, the fault occurred for 0.04 hours.

Service functions

Notes on safety

In all cases, only perform work on the fuel pump with the ignition off!

All work on the airbags must be carried out with the battery disconnected!

Connect and disconnect all BYTEFLIGHT control modules, sensors and generators only with the battery disconnected!

If a fiber-optic cable on the BYTEFLIGHT bus has to be repaired, it must be borne in mind that there may only be one join between the Safety and Information Module and a satellite. For this reason, no repairs may be performed on the fiber-optic cable between the Safety and Information Module and the the door satellites, as there is already a join with the door connector. In the case of a defect, the fiber-optic cable must be replaced!