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Home >> Saab >> 2010 >> 9-5 >> Repair and Diagnosis (Single Page) >> 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 Open/High Resistance

Testing the Serial Data Circuits for a Open/High Resistance

  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 greater than 130 Ω between each pair of serial data circuits. Verify that one pair of serial data circuits are greater than 130 Ω.
  3. If less 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 open circuit.
  6. Ignition OFF for 60 seconds, test for greater than 130 Ω between each pair of serial data circuits. Verify that one pair of serial data circuits are greater than 130 Ω.
  7. Repeat step  3 until one of the follow conditions are isolated:
    • An open/high resistance on the serial data circuit between 2 control modules
    • An open/high resistance on the serial data circuit between a control module and a terminating resistor
    • An open/high resistance terminating resistor
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