Circuit/System Verification: Notes

NOTE:

Review and understand how to use the Detected State section of the Data Bus Diagnostic Tool User Guide in service information web site prior to using the Data Bus Diagnostic Tool section in this diagnostic procedure.

Perform Circuit/System Verification using one of the following two methods:

Verifying the Serial Data Circuits using Data Bus Diagnostic Tool

Using schematics and vehicle build information, identify all low speed GMLAN devices the tested vehicle is equipped with, and each device location on the low speed GMLAN serial data bus.
Ignition ON/Vehicle In Service Mode.
From Data Circuit input selection, select Terminal 1 to test the low speed GMLAN serial data bus.
Start the test and verify that all applicable low speed GMLAN devices are displayed under the Control Module column of the Detected State tab.
- If all low speed GMLAN devices are not responding
  Refer to step 3 of Verifying the Serial Data Circuits using Digital Multimeter to test for a short to voltage or short to ground on the low speed GMLAN serial data circuit, or an open/high resistance between the X84 Data Link Connector and the first low speed GMLAN device or splice pack.
- If one or more low speed GMLAN devices are not responding
  Refer to Testing the Device Circuits to test the non-communicating low speed GMLAN device closest to the X84 Data Link Connector.
- Go to next step: If all low speed GMLAN devices are responding
All OK.