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HOMESERVICE MANUALSCHEVROLET2006CHEVY EXPRESS G2500, VAN CARGO, 6.6 2REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 1103 (DATA COMMUNICATION SYSTEM)DIAGNOSTIC INFORMATION AND PROCEDURESDTC U2099CIRCUIT/SYSTEM TESTING
2006 Chevrolet Chevy Express G2500, Van Cargo, 6.6 2

Circuit/System Testing

2006 Chevrolet Chevy Express G2500, Van Cargo, 6.6 2SECTION Circuit/System Testing
WARNING: This page is about a different car, the 2007 GMC Sierra and 2007 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
  1. With the ignition OFF, disconnect the harness connector at the EBCM, ESC module, and DSCC module one at a time. After each disconnect, clear the DTC, cycle the ignition key 3 times, then retest for the DTC. DTC U2099 should reset.
    • If the DTC does not reset, replace the last module disconnected.
  2. Ignition OFF, disconnect the harness connector at the BCM.
  3. With all modules disconnected, test for infinite resistance between the high speed GMLAN serial data wake up circuit and ground.
    • If less than infinite resistance, repair the wake up circuit for a short to ground.
  4. If all tests normal and DTC is current, replace the BCM.
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Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.