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Home >> Cadillac >> 2006 >> Escalade EXT >> Repair and Diagnosis >> External Pages >> Different car >> Section 1017 (Data Communication System) >> Diagnostic Information and Procedures >> Scan Tool Does Not Communicate With Low Speed GMLAN Device >> Circuit/System Testing
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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. Test for less than 1 ohm of resistance between the DLC ground circuit terminal 5 and ground.
    • If greater than 1 ohm, test the ground circuit for open/high resistance.
  2. Ignition OFF, disconnect the harness connector at splice pack SP 300.
  3. Ignition ON, with a scan tool, attempt to communicate with the instrument panel cluster (IPC). Communication should be available.
    • If no communication, disconnect the modules still connected to the DLC one at a time, starting with the furthest from the DLC and attempt to communicate after each disconnect. When communication occurs, test the serial data circuit for a short to ground and a short to voltage between the last module disconnected and the previous module disconnected. If the circuit tests normal, replace the last module disconnected. If no communication is possible, test the serial data circuit for a short to ground, a short to voltage or an open/high resistance between the last module disconnected and the DLC. If the circuit tests normal, replace the last module disconnected.
  4. Install a 3-amp fused jumper wire between pin A and pin M of the splice pack. Install another 3-amp fused jumper wire to pin L.
  5. Using the open end of the jumper wire at pin L, connect to splice pack terminals B through K and attempt to establish communications with each module connected to the splice pack, one at a time. Each module should be able to communicate.
    • If communications cannot be established with any module after connecting an individual module, replace the module that caused the no communication.
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