Warning lights

Service engine soon light on

This light is essentially the same as the check engine light on many vehicles, meaning the computer has detected a fault, usually emissions- or sensor-related, that should be looked at but generally isn't an emergency.

Difficulty
Easy
Time
15–30 minutes to check
DIY cost
$0–$20
Pro cost
$100–$300

Symptoms

  • 'Service engine soon' text or icon lit steady
  • Car generally drives normally
  • May notice slightly rough idle or reduced mileage

Likely causes

  • CommonLoose gas capOne of the most common and easiest triggers to fix.
  • CommonFailing oxygen sensorWear item that can affect fuel economy over time.
  • PossibleIgnition system component wearing out (spark plug, coil)Can trigger before a noticeable misfire develops.
  • PossibleEmissions component fault (EVAP, catalytic converter)Often follows an unresolved smaller issue.

What to do

  1. Check that the gas cap is tight and undamaged.
  2. Note any changes in how the car drives, sounds, or its fuel economy.
  3. Get the code read for free at most auto parts stores or with a personal code reader.
  4. Write down the exact code before doing anything else.
  5. Look up what that code typically means for your specific make and model.
  6. If the car drives fine, plan a repair visit soon rather than waiting indefinitely.
  7. Have a mechanic confirm the diagnosis before replacing parts.

Tools and parts

  • OBD-II code reader (or free scan at a parts store)

When to call a pro

See a mechanic if the light doesn't clear after checking the gas cap, or if you notice the car running rough.

Safety

Generally low risk

Generally low risk for a careful person. Stop if anything looks different from what this guide describes.

Related guides

Operator provides AI-generated troubleshooting information. It can be wrong. For safety-critical, electrical, gas, structural, medical, automotive safety, or other high-risk problems, consult a qualified professional.