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A module that has stopped receiving messages it depends on from elsewhere on the vehicle network. The fault is reported by the module that noticed, which is almost never the module that failed — and that is the whole difficulty.

Chassis systems are unusually exposed to this because they cannot work alone. Stability control asks the engine to reduce torque and the transmission to hold a gear, so it depends on those modules answering. Every chassis sensor can be perfect and the system still shut down because a conversation stopped.

Read all modules, not just the one that complained. A single module that has lost power, lost its ground, or failed will produce communication codes in every other module that was expecting to hear from it — so the module with the fewest codes of its own is often the culprit.

Physical causes dominate: a corroded connector, a chafed bus wire, water in a connector at a body-to-door or body-to-tailgate crossing, or a module unplugged and not reconnected during other work. Low system voltage produces it too, and does so intermittently, which is worse.