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Home >> Chevrolet >> 2006 >> Chevy Express G3500, Van Passenger Extended >> Repair and Diagnosis >> External Pages >> Different car >> Section 901 (Data Communication System) >> Diagnostic Information and Procedures >> Scan Tool Does Not Communicate with Class 2 Device >> Circuit/System Testing
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Circuit/System Testing

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2007 GMC Savana Special, 2007 GMC Savana Camper Special, 2007 GMC Savana, 2007 Chevrolet RV Cutaway, and 2007 Chevrolet Cutaway. However, it is still accessible from the selected car via links, so may be relevant.
  1. Test for less than 1.0 ohm of resistance between the DLC ground circuit terminal 5 and ground.
    • If greater than 1.0 ohm, test the ground circuit for open/high resistance.
  2. Ignition OFF, disconnect the harness connector (splice pack comb) at SP 205. Install a 3-amp fused jumper wire between SP 205 pin A and pin M, harness side.
  3. Ignition ON, with a scan tool, attempt to communicate with the body control module (BCM). Communication should be available.
    • If no communication, test the serial data circuit for a short to ground, a short to voltage or an open/high resistance between the BCM and the DLC. If the circuit tests normal, replace the BCM.
  4. Install another 3-amp fused jumper wire to SP 205 pin A, harness side.
  5. With BCM communications established, use the other end of the jumper wire to connect all other pins, harness side, one at a time and verify that communication remains available to the BCM.
    IMPORTANT: Allow communications for 5 seconds after connecting a module with the jumper to determine if communication is interrupted or not.
    • If communication is interrupted after connecting an individual module at SP 205, test the serial data circuit between SP 205 and the last module connected for a short to ground and short to voltage. If the circuit tests normal, replace the module that caused no communication.
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