Check Engine Light On (Solid, Not Flashing) — Causes & Next Steps

What's happening

A steady CEL means the engine computer has detected a fault and stored a diagnostic trouble code (DTC). The light alone tells you almost nothing — the stored code does. The most common single trigger across the entire fleet is a loose gas cap (EVAP leak), followed by oxygen sensors, catalytic converter codes, and misfires.

You might also notice

• May be no other symptoms at all
• Slight loss of fuel economy
• Subtle changes in idle quality

Likely causes (most common first)

1. Loose or failing gas cap (EVAP codes — start here, it is free)
2. Aged oxygen sensor
3. Failing catalytic converter
4. Vacuum leak causing lean codes
5. Misfire (with the light steady, severity is usually moderate)
6. Coolant temperature / thermostat issues

What to check first

1. Tighten the gas cap until it clicks; drive a few cycles, see if light clears
2. Read the code with a Bluetooth OBD2 adapter and a free app like AXLY.pro
3. Note any drivability changes — even subtle ones help diagnosis

Common OBD2 codes for this symptom

Don't have the code yet? Look up your code or read it with AXLY.pro.

Can I keep driving?

Yes, short-term. But do read the code soon — some codes are cheap fixes that get expensive if ignored (a $40 O2 sensor left alone can kill a $1,500 catalyst).

Confirm with the actual code

Symptom-based diagnosis narrows the field — reading the actual stored code finishes the job. AXLY.pro is a free iPhone app that pairs with any Bluetooth OBD2 adapter and reads every stored DTC.