What is the check engine light symbol supposed to be?
The check engine light symbol is a stylized engine icon—the silhouette of an internal combustion engine—used by the vehicle’s onboard diagnostic system to signal a fault. In most cars it’s amber or yellow, though the exact shape and color can vary by manufacturer. The symbol is officially known as the Malfunction Indicator Lamp (MIL).
What the symbol looks like
Across automakers the MIL keeps to a simple engine silhouette, but the rendering can differ. Common traits include:
- A simplified silhouette of an engine block, often with a curved line suggesting exhaust or intake paths.
- Color is typically amber or yellow when the fault is active; red or a flashing light usually indicates a more urgent condition.
- Some brands place the words “Check” or “MIL” near the icon or display a slightly different variant of the engine glyph.
In essence, the symbol is an engine icon. Its exact design varies, but the meaning remains the same: a diagnostic trouble code has been detected that should be diagnosed and repaired.
What it means and what to do
When the MIL lights up, the vehicle’s computer has detected a fault in the engine, emissions system or related components. The recommended response depends on whether the light is steady or flashing:
- Steady light: A fault has been detected. Have the vehicle diagnosed with a scan to retrieve trouble codes and determine the necessary repair.
- Flashing light: A misfire or severe issue is occurring. Stop driving safely as continued operation can damage the catalytic converter or engine; arrange immediate service or towing if necessary.
- First steps you can take before a repair: check for a loose or damaged gas cap, look for obvious wiring issues, and note any symptoms such as rough idle, reduced power or poor fuel economy.
- Getting a code read: use an OBD-II scanner, or visit an auto parts store or mechanic to retrieve the codes and interpret them.
- Repair and reset: fix the identified fault and have the codes cleared so the MIL can go off; the light may return if the fault recurs or the system detects a new issue.
Note: The presence of a MIL doesn’t always indicate severe danger, but it should be diagnosed promptly to avoid potential damage or increased emissions.
Common causes
Several issues frequently trigger the MIL. The following list covers what you’re most likely to encounter:
- Loose or faulty gas cap.
- Faulty oxygen sensor (O2 sensor) or catalytic converter problems.
- Malfunctioning Mass Air Flow (MAF) sensor or manifold vacuum leaks.
- Ignition system problems such as worn spark plugs or bad ignition coils.
- Evaporative (EVAP) system leaks or related faults.
Because the codes point to a range of potential issues, a diagnostic scan is the best way to pin down the exact cause and the necessary repair.
Summary
The check engine light symbol is the engine silhouette used as the Malfunction Indicator Lamp to signal a fault detected by the OBD-II system. While the icon’s exact look can vary by brand, its purpose is consistent: prompt diagnosis and repair to protect engine performance and emissions. If the light is flashing, treat it as urgent; if steady, arrange a diagnostic and address the underlying issue.
