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Diagnostic System Check

The diagnostic system check determines:

  1. Using scan tool, 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  under SYSTEM TESTS.
  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  under SYSTEM TESTS.
  3. Select "body diagnostics" on the scan tools menu. Select "SIR UART data line information". Access any DTCs that may be present. If no DTCs are present, go to next step. If any DTCs are present, diagnose as necessary. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If there is no communication with the scan tool, see SCAN TOOL DOES NOT COMMUNICATE WITH UART DATA LINE  under SYSTEM TESTS.
  4. Select "body diagnostics" on the scan tools menu. Select "E and C data line" and access any DTCs that may be present. If no DTCs are present, go to next step. If any DTCs are present, diagnose as necessary. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If there is no communication with the scan tool, see SCAN TOOL DOES NOT COMMUNICATE WITH ENTERTAINMENT & COMFORT DATA LINE  under SYSTEM TESTS.
  5. Establish communication with the EBCM. If the vehicle is 15,000 GVW or more, access any DTCs that may be present. If no DTCs are present, go to next step. If any DTCs are present, diagnose as necessary. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If there is no communication with the scan tool, see SCAN TOOL DOES NOT COMMUNICATE WITH EBCM  under SYSTEM TESTS.
  6. Establish communication with the PCM/VCM. Access any DTCs that may by present. If no DTCs are present, go to next step. For DTC U1026, see DTC U1026: LOSS OF TRANSFER CASE SHIFT CONTROL MODULE CLASS 2 COMMUNICATION  under DIAGNOSTIC TESTS. For DTC U1041 see DTC U1041: LOSS OF EBCM COMMUNICATION  under DIAGNOSTIC TESTS. For DTC U1192 see DTC U1192: LOSS OF EVO/PASSLOCK™ CLASS 2 COMMUNICATION  under DIAGNOSTIC TESTS. 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  under SYSTEM TESTS.
  7. Establish communication with the ATCM. Access any DTCs that may be present. If no DTCs are present, go to next step. For DTC U1016, see DTC U1016: LOSS OF COMMUNICATIONS WITH PCM/VCM  under DIAGNOSTIC TESTS. For DTC U1041, see DTC U1041: LOSS OF EBCM COMMUNICATION  under DIAGNOSTIC TESTS.
  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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