Check Engine Light On? What It Usually Means (and What to Do Next)

The check engine light (also called the MIL—malfunction indicator lamp) is one of the most searched questions Australians ask mechanics. It can be anything from a loose fuel cap to an issue that could damage the engine if ignored. The trick is knowing what the light is telling you and what to do safely.

Steady light vs flashing light

• Steady check engine light: the car has detected a fault and stored a code. You can usually continue driving carefully, but you should book a diagnostic check soon.
• Flashing check engine light: treat this as urgent. A flashing MIL often indicates an active misfire, which can overheat the catalytic converter and lead to costly repairs. Reduce load, avoid hard acceleration, and pull over when safe if the car is running rough.

Common causes we see

While every car is different, typical triggers include:

• Loose/failed fuel cap or evap system fault
• Oxygen sensor or other emissions-related sensor issues
• Ignition misfire (spark plugs, coils, leads)
• Air intake/vacuum leaks or dirty airflow sensors
• Fuel system issues (pressure, injectors)
• Turbo/boost control faults on turbocharged vehicles

What you can check yourself (quick and safe)

1. Tighten the fuel cap until it clicks (if your vehicle has one).
2. Check the temperature gauge—if it’s overheating, stop driving and get it inspected.
3. Pay attention to symptoms: shaking, lack of power, odd noises, strong fuel smell, smoke, or stalling.

What not to do

Avoid clearing the light with a cheap scanner and hoping it’s “gone for good”. Clearing codes can hide valuable clues and may delay the real fix. Also avoid continuing to drive hard if the car feels rough—extra heat and unburnt fuel can turn a small issue into a bigger one.

How a proper diagnosis works

At Your Local Mechanical (YLM), we start with a scan to read fault codes and live data, then confirm the cause with targeted testing (for example, checking ignition performance, smoke-testing for leaks, or verifying sensor readings). Codes point to a system, not always a part—so testing first helps prevent unnecessary replacements.

Why acting early saves money

Small issues like a weak coil, split hose or sensor fault are often straightforward when caught early. Left too long, they can cause secondary damage, poor fuel economy, and failed emissions components.

When to stop and call for help

If the light is flashing, the engine is running very rough, the car drops into limp mode, or you see a red oil/overheat warning, stop driving and arrange assistance.

Tip for faster diagnostics

Note what was happening when the light came on (after refuelling, during towing, on a hill, in heavy rain). Those clues can speed up testing.

If your check engine light is on, book in with YLM and we’ll translate the codes into plain English, give you clear options, and get you back on the road with confidence.