Steady: the on-board diagnostics found a problem in the engine or emissions system. You can keep driving, but drive less, avoid high speeds and get it checked soon; first make sure the gas cap is tight (EPA, Honda). Flashing: a severe misfire that can damage the engine and the emissions system. Slow down and get service as soon as possible; Honda says to park safely and let the engine cool (EPA, Honda).
What the check engine light means
The EPA’s on-board diagnostics (OBD) rules cover cars and light trucks from the 1994 model year on: a computer watches the engine and emissions controls, and when it finds a fault it stores a code and turns on a dashboard light. The light is usually yellow and reads “Check Engine” or “Service Engine Soon,” or shows an engine symbol (EPA).
The EPA puts it plainly: the light tells you the car needs service, not that it needs to stop. Ford describes a steady light as an error the diagnostics have found in the emission control system, and Honda as a problem with the engine emissions control system.
If the light is steady
- Don’t panic. The car will keep running; you can still drive safely, but should drive as little as possible (EPA).
- Check the gas cap when you stop. A loose or missing cap lets fuel vapor escape, which the system detects (EPA).
- Drive gently. Honda says to avoid high speeds until the car has been inspected.
- Get the code read. A shop or dealer connects a scan tool to read the codes that point to the problem (EPA). Our trouble code lookup is coming soon.
If the light is flashing
A flashing light means a severe engine misfire (EPA, Ford, Honda). Honda warns that driving with the light on can damage the emissions control system and the engine.
- Reduce speed and get service as soon as possible (EPA).
- Honda’s steps: park in a safe place away from anything flammable and wait at least 10 minutes with the engine off, until it cools. If the light flashes again when you restart, drive to the nearest dealer at 31 mph (50 km/h) or less.
The gas cap, and why the light can go off by itself
If the cap wasn’t tightened after filling up, the system can detect the vapor leak and turn the light on. Tighten it, and the light should go off within a few days (EPA). More generally, if the system checks the same part three times in a row and no longer finds the problem, it turns the light off itself (EPA). That doesn’t mean the system is faulty, but if the light keeps coming back, have the code read.
Questions people ask
Is it safe to drive with the check engine light on?
If it’s steady, yes, for now: drive less and avoid high speeds until it’s checked (EPA, Honda). If it’s flashing, slow down and get service as soon as possible (EPA).
Why is my check engine light on?
The diagnostics have found a fault in the engine or emissions system. It can be as simple as a loose gas cap (EPA); the stored code tells a technician where to look.
Why is my check engine light flashing?
The engine is misfiring badly (EPA, Ford, Honda). Slow down, and follow your manual; Honda says to pull over and let the engine cool.
Will the check engine light turn off by itself?
Yes, if the problem goes away: after three checks in a row without finding it, the system switches the light off (EPA).
How long after tightening the gas cap does the light go off?
Within a few days of driving, if the cap was the problem (EPA).
Sources
- U.S. EPA, Frequently Asked Questions About On-Board Diagnostics (EPA 420-F-97-003, 1997): usually yellow; service, not stopping; flashing means a severe misfire; the gas cap; three checks in a row; OBD from the 1994 model year; how the light is labeled.
- U.S. EPA, What To Do With the Check Engine Light (EPA 420-F-00-041, 2000): don’t panic; drive less; check the gas cap; blinking means a severe problem such as a misfire; scan tool codes.
- Honda, 2023 Integra Owner’s Manual, If the Malfunction Indicator Lamp Comes On or Blinks: emissions control problem; misfire; avoid high speeds; cool for 10 minutes; 31 mph to the dealer.
- Ford, What do the warning and indicator lights in my Ford mean?: an emission control error; flashing for a misfire.