#fault codes
4 posts in Car Diagnostics blog about "fault codes" — OBD-II diagnostics, DTC codes, repair. ← All posts
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Pending, stored, and permanent: three kinds of code and why it matters
Not all codes are equal: one warns, one has already lit the lamp, and one cannot be cleared at all. The difference and how to use it.
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Clearing codes: when it helps and when it hurts
The clear button looks like a solution while often destroying the evidence. When clearing is appropriate and what disappears with the code.
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Anatomy of a fault code: what every character in P0301 actually means
The five characters are not arbitrary. The letter names the system, the first digit says whether it is standard or manufacturer-specific, the second names the subsystem, and the last two pin it down. After this, codes read without a lookup table.
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When the scanner lies: ghost codes, false triggers, and why "a code" is not "a broken part"
The code points at a sensor and the sensor is fine. The code vanishes and returns a week later. Why that happens, how to tell a real fault from a side effect, and why the freeze frame decides more than the code does.