Type in a code like P0420 to get a plain-language explanation, whether it's safe to keep driving, the likely causes, how to diagnose it, and typical repair costs.
A code's first letter tells you the system: P for powertrain (engine and transmission — by far the most common), C for chassis (brakes, steering, suspension), B for body (airbags, seatbelts, comfort electronics), U for network (communication between the car's computers). The second character is usually 0, meaning it's a generic code defined the same way across every manufacturer — the remaining digits identify the specific fault.
The short code name (e.g. "Catalyst System Efficiency Below Threshold") is a standardized industry fact, the same everywhere. Everything else on this page — what it means in plain terms, the likely causes, how to check it, what it typically costs to fix — is written by our editorial team, not copied from a manufacturer spec or another site.
It depends on the specific code. A steady check engine light with no other symptoms is usually safe to drive on for a while, though you should get it checked soon. A flashing check engine light, or any warning light alongside unusual noises, smells, or handling changes, means you should stop driving and get the car checked immediately — continuing to drive can turn a cheap fix into an expensive one.
The five-character code itself and its short official name (e.g. "P0420 — Catalyst System Efficiency Below Threshold") are standardized and identical everywhere. Everything beyond that — the plain-language explanation, likely causes, and repair guidance — is written independently by each site, which is why the depth and accuracy varies. We write ours from scratch rather than copying another source.
Yes, and it's a reasonable first step for minor codes (like a loose fuel cap triggering an EVAP code) — clear it, drive normally, and see if it returns within a few drive cycles. For anything flagged as "stop driving" or involving safety systems, don't just clear it — diagnose and fix the underlying issue first.