The check engine light turns on when the computer finds a fault it cannot fix. Solid means have it checked soon, and flashing means a misfire severe enough to damage the converter. A scan gives a code, and a diagnosis finds the cause.
Key takeaways
- Flashing means act now.
- A code is a clue.
- A lit light fails smog.
What the light is
The malfunction indicator lamp tells you the engine, emissions or transmission computer has stored a fault. Read our guide to flashing versus solid lights for what to do right away.
Why a scan is not a diagnosis
A free code read tells you the code. A diagnosis tests the system. We explain the difference in our diagnostic guide.
What it costs
Costs vary with the symptoms. Our diagnostic cost guide explains what is included and what to ask.
Common causes
Gas caps, spark plugs and coils, sensors and evap leaks cause most lights. See our guides on gas caps, misfires and common codes.
Rough running and stalling
If the light comes with a rough idle or stalling, read our guide on rough idle and stalling.
Smog and warning lights
A lit light fails smog. Our smog and light guide explains. For other dashboard lights, see our dashboard warning lights guide. Buying a used car? Read the pre-purchase inspection guide.
A short routine when the light appears
Note the date, whether the light is steady or flashing and any change in how the car drives. Check the gas cap. Avoid heavy loads and towing. Then book a diagnosis rather than clearing the code. This routine gives the technician useful data and avoids the common mistake of resetting the system and losing the evidence. It also protects your smog timeline, because a cleared code leaves monitors not ready.
In this guide
- Flashing vs Solid Check Engine Light: What to Do
- What a Diagnostic Scan Really Tells You (and Does Not)
- Check Engine Light Diagnostic Cost: What You Pay For
- Can a Loose Gas Cap Turn On the Check Engine Light?
- Engine Misfire: Spark Plugs, Coils and Other Causes
- Car Idles Rough or Stalls: What Causes It
- OBD2 Codes Explained: P0420, P0171 and P0455
- Dashboard Warning Lights: Which Mean Stop Now
- Buying a Used Car in Bakersfield: Inspect First
Need help in south Bakersfield?
Questions about check engine light? Read our Check Engine Light page, call (661) 599-9098 or request a time. Peña's Auto Electric, Smog & Repair, 303 Taft Hwy, Suite B, Bakersfield, CA 93307. Mon to Fri 9:30 AM to 5:30 PM, Sat 8 AM to 1 PM.
Frequently asked questions
Can I drive with the light on?
Short careful trips if steady. Not if flashing.
Why did the light come on?
A scan and test tell.
Will it turn off by itself?
Sometimes, if the fault was temporary.
Is a free scan enough?
It gives codes, not the cause.
Related reading
- Flashing vs Solid Check Engine Light: What to Do
- What a Diagnostic Scan Really Tells You (and Does Not)
- Check Engine Light Diagnostic Cost: What You Pay For
- Can a Loose Gas Cap Turn On the Check Engine Light?
- Engine Misfire: Spark Plugs, Coils and Other Causes
- Car Idles Rough or Stalls: What Causes It
- OBD2 Codes Explained: P0420, P0171 and P0455
- Dashboard Warning Lights: Which Mean Stop Now
- Buying a Used Car in Bakersfield: Inspect First
Sources
- California Bureau of Automotive Repair, Smog Check program and consumer information