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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 Short to Ground

Testing the Serial Data Circuits for a Short to Ground

  1. Ignition OFF, disconnect the harness connectors with the mid speed or chassis high speed serial data circuits at an easily accessible control module.
  2. Ignition OFF for 60 seconds, test for less than 100 Ω between the serial data circuits and ground. Verify that one or more serial data circuits are less than 100 Ω.
  3. If greater than the specified range for all serial data circuits, replace the control module that was disconnected.
  4. Disconnect the harness connectors with the mid speed or chassis high speed serial data circuits at another control module, in the direction of the circuit shorted to ground.
  5. Ignition OFF for 60 seconds, test for less than 100 Ω between the serial data circuits and ground. Verify that one or more serial data circuits are less than 100 Ω.
  6. If greater than the specified range for all serial data circuits, replace the control module that was just disconnected.
  7. Repeat step  3 until one of the follow conditions are isolated:
    • A short to ground on the serial data circuit between 2 control modules
    • A short to ground on the serial data circuit between a control module and a terminating resistor
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