The break at the beginning of a LIN header is deliberately longer than an ordinary data bit. It should not be confused with a permanent short.
Interpreting the evidence
When reviewing a scope image, widen the recording enough to see whether the line returns and a complete frame follows. A cropped image of the low interval can make normal framing look like a wiring failure. Compare repeated events under the same command.
Keep this evidence
Include the full frame, time scale and the name of the function being operated.
A line stuck low beyond the expected sequence remains a different concern. The complete recording, not the pulse in isolation, guides that distinction.
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Technical background from NXP. The referenced design explains the principle; the vehicle-specific procedure determines the repair.
Related reading — LIN header present but the expected device does not answer. Browse all vehicle-electronics diagnostic notes or return to the repair library.