The check engine light is the most profitable light in your mechanic's shop — because most drivers walk in blind. Here's the truth: the five most common causes range from a $0 fix (loose gas cap) to a $30 part you can swap in your driveway. Diagnose first, then decide.
Not sure this is your exact problem?Point your camera at it — SpotFix AI diagnoses it free in seconds, with a step-by-step AR guide for your exact model.
Scan It FreeSolid = not urgent, diagnose at your convenience. Flashing = stop driving soon; an active misfire is dumping fuel into the exhaust.
A loose or cracked gas cap triggers the evap-system code behind a surprising share of check engine lights. Click it three times and drive a day or two — the light may clear itself.
Every auto parts store (AutoZone, O'Reilly) reads codes free, or buy a $20 Bluetooth OBD-II dongle. You'll get a code like P0420 or P0171.
Scan the code readout with SpotFix AI — it explains the code in plain English, the likely part, the DIY difficulty, and the fair repair price so no one can invent a number.
O2 sensor (~$22–$60, one wrench), spark plugs (~$40 a set), mass airflow sensor cleaning (a $8 spray). The app's AR guide shows exactly where each part lives on your engine.
After the fix, clear the code with your scanner and drive a full cycle. If it stays off, you're done — for a fraction of the quote.
50,000+ repairs diagnosed · 92% accuracy · users save $420 on average. Free on iOS.