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Circuit/System Testing

  1. With the ignition OFF, disconnect the harness connector at each module on the circuit one at a time. After each disconnect, retest for current DTCs. DTC U2099 should remain current.
    • If the DTC becomes history, replace the module disconnected before the DTC became history.
  2. Ignition OFF, disconnect the harness connector X3 at the BCM.
  3. With the harness connector at the modules disconnected, test for infinite resistance between the BCM high speed GMLAN serial data wake up circuit terminal X3, 19 and ground.
    • If less than the specified value, test the wake up circuit for a short to ground.
  4. Test for less than 1 Ω between the BCM high speed GMLAN serial data wake up circuit terminal X3, 19 and each serial data wake up circuit terminal at each disconnected module connector.
    • If greater than the specified value, test for an open/high resistance in the serial data wake up circuit. If all circuits test normal and the DTC is current, replace the BCM.
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