Learn how to scan for OBD2 trouble codes, record freeze-frame data, distinguish a code from a confirmed fault, and decide when professional diagnosis is needed.
A safe first-response guide to a check engine light: warning severity, recording OBD2 codes, recognising urgent symptoms and avoiding unnecessary part replacement.
Understand what OBD2 code P0420 means, which faults can trigger it, what to check before replacing a catalytic converter, and when to seek a technician.
Understand the difference between stored, pending and permanent OBD2 trouble codes, why a code may return, and why clearing it is not the same as fixing the fault.