Tag
#clearing codes
4 posts in Car Diagnostics blog about "clearing codes" — OBD-II diagnostics, DTC codes, repair. ← All posts
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Code aging: how a fault clears itself after 40 warm-up cycles
Codes do not stay forever. The ECU counts successful warm-ups and eventually forgets — which is useful to know before you buy a used car.
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Mode 0A permanent DTCs: the codes you cannot clear
Disconnecting the battery clears normal codes. It does not touch these, and that is exactly why they exist.
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OBD-II Modes 03 and 04: reading and clearing codes correctly
One mode reads confirmed codes, the other erases far more than most people realise. Knowing exactly what Mode 04 destroys is what stops you clearing away your own evidence.
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Why the check engine light comes back after clearing
Clearing a code does not repair anything. Understanding the drive-cycle logic behind when the light returns tells you whether a repair worked or merely delayed the verdict.