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Home › GMC › 1998 › Yukon 4WD › Repair and Diagnosis › Accessories & Equipment › Communication Devices › Data Link Communications System › System Tests › Diagnostic System Check

Diagnostic System Check

  1. Connect a scan tool and attempt to make contact with any of the modules on the vehicle. If the main menu appears on the scan tool, go to next step. If the screen is blank or there is no power to the scan tool, see SCAN TOOL INOPERATIVE .
  2. Select "diagnostics circuit check, Class 2 DTC check" on the main menu. The scan tool should list the PCM/VCM, ABS/TCS, VTD/EVO and ATCM (if the vehicle has an automatic transfer case). If the scan tool lists all modules, go to next step. If some or all of the modules are not listed, see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DATA LINE .
  3. Select "body diagnostics" on the scan tools menu. Select "SIR UART data line information". Access any DTCs that may be present. If there is no communication with the scan tool, see SCAN TOOL DOES NOT COMMUNICATE WITH UART DATA LINE .
  4. Select "body diagnostics" on the scan tools menu. Select "E and C data line" and access any DTCs that may be present. If there is no communication with the scan tool, see SCAN TOOL DOES NOT COMMUNICATE WITH ENTERTAINMENT & COMFORT DATA LINE .
  5. Establish communication with the EBCM. If the vehicle is 15,000 GVW or more, access any DTCs that may be present. If there is no communication with the scan tool, see SCAN TOOL DOES NOT COMMUNICATE WITH EBCM .
  6. Establish communication with the PCM/VCM. Access any DTCs that may by present. For DTC U1026, see DTC U1026: LOSS OF TRANSFER CASE SHIFT CONTROL MODULE CLASS 2 COMMUNICATION . For DTC U1041 see DTC U1041: LOSS OF EBCM COMMUNICATION . For DTC U1192 see DTC U1192: LOSS OF EVO/PASSLOCK™ CLASS 2 COMMUNICATION . If there is no communication with the scan tool, see SCAN TOOL DOES NOT COMMUNICATE WITH PCM  or SCAN TOOL DOES NOT COMMUNICATE WITH VCM .
  7. Establish communication with the ATCM. Access any DTCs that may be present. For DTC U1016, see DTC U1016: LOSS OF COMMUNICATIONS WITH PCM/VCM . For DTC U1041, see DTC U1041: LOSS OF EBCM COMMUNICATION .
  8. Establish communication with the EVO/Passlock™ module. Access any DTCs that may be present. For DTC U1016, see DTC U1016: LOSS OF COMMUNICATIONS WITH PCM/VCM . For DTC U1255, see DTC U1255: SERIAL DATA LINE MALFUNCTION .
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