The check engine light turns on and your first question is always the same: can I still drive? The answer depends entirely on how the light is behaving.
Steady light vs. flashing light
Steady check engine light
A steady light means a fault has been logged but is not actively causing severe damage right now. Generally safe to drive 50–100 miles to reach a shop. Schedule a diagnostic within a few days.
Flashing check engine light
Stop driving as soon as safe. A flashing light means an active engine misfire sending raw fuel into the catalytic converter — which can be destroyed within minutes. Call a tow rather than driving to a shop.
Codes ranked by urgency
- Stop immediately: P0217 (overheating), P0520 (oil pressure), any flashing CEL
- 24–48 hours: P0300 misfire (steady), P0171 lean, P0087 low fuel pressure
- 1–2 weeks: P0420 catalyst, P0442 EVAP, P0128 thermostat
What happens if you ignore it for months?
- Automatic emissions test failure in most states
- Cascading damage — a lean condition stresses pistons, a misfire destroys the cat converter
- Worse fuel economy on almost every active fault
Read your code first at myobdcode.com/check-engine — it tells you the urgency level before you decide whether to drive.