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Home >> Saab >> 2010 >> 9-5 >> Repair and Diagnosis >> Accessories & Equipment >> Communication Devices >> Bus And Diagnostics Communication >> Fault diagnosis, fault codes >> DTC U0074: Control Module Communication Bus B Off >> Circuit/System Testing >> Testing the Serial Data Circuits for a Short between the Circuits

Testing the Serial Data Circuits for a Short between the Circuits

  1. Ignition OFF, disconnect the harness connectors with the mid speed or chassis high speed serial data circuits at an easily accessible control module, that is not communicating.
  2. Ignition OFF for 60 seconds, test for less than 110 Ω between each pair of serial data circuits. Verify that one pair of serial data circuits are less than 110 Ω.
  3. If greater than the specified range for each pair of serial data circuits, replace the control module that was disconnected.
  4. Connect the harness connectors at the control module that was disconnected.
  5. Disconnect the harness connectors with the mid speed or chassis high speed serial data circuits at another control module, in the direction of the circuits shorted together.
  6. Ignition OFF for 60 seconds, test for less than 110 Ω between each pair of serial data circuits. Verify that one pair of serial data circuits are less than 110 Ω.
  7. If between the specified range for each pair of serial data circuits, replace the control module that was just disconnected.
  8. Repeat step  3 until one of the follow conditions are isolated:
    • Serial data circuits shorted together between 2 control modules
    • Serial data circuits shorted together between a control module and a terminating resistor
    • A shorted terminating resistor
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