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.
Class 2 Communication Malfunction: Description
Modules connected by class 2 serial data circuit monitor communications during normal vehicle operation. Operating information and commands are exchanged between modules. When a module receives a message for a critical operating parameter, receiving module records identification number of sending module for state of health monitoring. Critical operating parameter, if not received, requires receiving module to use default values for that parameter. If a module does not associate an identification number with at least one critical parameter within 5 seconds of beginning serial data communication, DTC U1000 will set, if DTCs U1300 or U1301 do not have current status. DTC U1000 will set only once if more than one critical parameter does not have an identification association.
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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.