Don’t Clear That Check Engine Light—This $100 Tool Can Save You a Failed Smog Test

The “check engine” light is the most annoying orange icon in America. Half the time the car feels fine, and the other half you’re about to fail emissions or get stranded. A good Onboard Diagnostic 2 (OBD2 – the 2 just points to an updated standard) scanner puts you back in control because it tells you what the car thinks is wrong—before you waste money or show up for a test and get bounced. It also helps you decide if it’s safe to keep driving.

This got more serious in 2025. California tightened its OBD readiness rules on October 1...