Glossary
check-engine light
The check-engine light means the computer has found a fault and stored a code, so it is a drive-to-a-scan-tool warning rather than a stop-right-now one.
The check-engine light is the engine computer's way of saying that a fault was detected and a code was stored. It is not a diagnosis and it does not name a part: the computer watches the sensors and the systems it can test, and when a reading stays outside the range it expects, it files the fault and lights the lamp. The code is then read through the OBD-II port.
The light's two behaviors carry different urgency, and that distinction is the one exam questions probe. A steady light means the fault is stored and the car can be driven to a scan tool. A flashing light means an active misfire is sending unburned fuel into a hot catalytic converter, where it can burn and destroy it — the driver should reduce power, avoid the conditions that provoke it, and stop as soon as it is safe.
What the light is not is the oil-pressure light. The check-engine light is about a fault the computer found; the oil-pressure light is about oil pressure already lost, and it means shut the engine off now.
Taught in
Related terms
- OBD-II — OBD-II is the standard under-dash diagnostic socket that lets a scan tool talk to the engine computer and read the fault codes it has stored.
- oil-pressure light — The oil-pressure light warns that oil is not circulating under pressure, which is why it means stop the engine rather than wait and check the level later.
Source: Official ASVAB — subtest descriptions (what each subtest asks) and the CAT-ASVAB scored-question counts (accessed 2026-09)