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 Gateway 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. 9) 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 have to generate a fault memory entry if a message from the transmitting control module fails. If, for example, the Safety and Gateway Module is no longer transmitting message 9, the fault memory entry ”Message (9) from Safety and Gateway Module missing” is created in the SBSL (left B-pillar satellite), SBSR (right B-pillar satellite), TMFA (door module, driver) and TMBF (door module, passenger).

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 Gateway Module (SGM) or
    
  • Fiber-optic cable between receiving control module and SGM 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 Gateway Module (SGM) or
    
  • Fiber-optic cable between transmitting control module and SGM 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 Gateway 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 TMFA missing” fault is stored in one control module (e.g. SBSL). Use the following procedure:

• Look for the row in the Table that contains the transmitting control module (TCU) TMFA with message (1).
  
• From the Table, establish which control modules are receiving this message. For the above example, these are the control modules SBSL and TMFA.
  
• Display the fault memory list of the control modules SBSL and TMFA 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 TMFA missing” fault is entered in all receiving control modules SBSL and TMFA, then there are the following possible faults:
  
  • Transmitting control module TMFA
    
  • Safety and Gateway Module (SGM)
    
  • Fiber-optic cable between TMFA and SGM
    
  • Plug-in connections at the two control modules
    
• If the ”Message (1) from TMFA missing” fault is only entered in one receiving control module, e.g. SBSL, then there are the following possible faults:
  
  • Receiving control module SBSL
    
  • Safety and Gateway Module (SGM)
    
  • Fiber-optic cable between SBSL and SGM
    
  • 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.
  

Service functions

Notes on safety

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 in a fiber-optic cable. If there is already a join due to a door connector, the fiber-optic cable must not be repaired. In the case of a defect, the fiber-optic cable must be replaced!