Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Communication Pre-Diagnostic Procedure
Verify that the battery is fully charged before attempting any diagnostic procedure.
- Check for any Service Bulletins/Recalls that may apply.
- With the scan tool, read all active DTCs from all modules.
- Check for BCM configuration, CAN Bus, VIN Missing/Mismatch, battery or ignition related DTCs. If any DTCs are present, perform the appropriate diagnostic procedure before proceeding.
If none of the above apply, pick the one below that best describes your situation:
If you were referred to this procedure from another module Diagnostic Information and no other modules are reporting a lost communication DTC against that module:
- Refer to DIAGNOSIS AND TESTING
and perform the Lost Communication with the module that was referenced.NOTE:
Some DTC numbers and naming may not match exactly to those listed in the BCM. Select the DTC that matches the closest.
If more than one module is reporting a communication DTC against one module:
- This is an indication of a communication problem with that module. Refer to DIAGNOSIS AND TESTING and perform the No Response from the module that is being reported from the other modules.
If the reported DTC is not Active:
- Refer to DIAGNOSIS AND TESTING and perform the Stored Lost Communication DTCs diagnostic procedure.
- Refer to DIAGNOSIS AND TESTING
and perform the Lost Communication with the module that was referenced.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.