Diagnosis bus defective

Disturbances in data transfer on the diagnostic bus (TxD link) may be attributed to the following faults:

control module emits interference

A control module disturbs data traffic

• Briefly disconnect and connect battery. Then repeat test step ”test diagnostic bus 01”.
  
• No further measures are necessary if fault no longer occurs within the current diagnostic procedure.
  
• If the fault reoccurs, determine faulty control module by removing one after the other the fuses of all control modules connected to the diagnostic bus (refer to schematic). Repeat the test step ”test diagnostic bus 01” after each fuse.
  If data transfer to the other control modules is OK, the control module with no current applied will disturb data traffic. The control module concerned should be replaced (refer to currently applicable Service Information. The fault may be in the software and can also occur with new control modules).
  

Line faulty

The data link (TxD link) has a break or short to positive or ground

• Check line with ”preset measurement - line test” and repair if necessary.
  
• A short in the line may be caused by a faulty control module. Therefore disconnect all control modules one after the other and determine faulty control module by the presence of a short.
  

control module faulty

Proceed as follows if the data link is OK and no fault was found by unplugging the fuses:

• Disconnect one after the other all control modules which are connected to the diagnostic bus (see schematic). Repeat test step ”test diagnostic bus 01” after every disconnected control module.
  If data transfer to the other control modules is OK, the disconnected control module will disturb data traffic. The control module concerned should be replaced.