Amber · Investigate soon
Engine management / check engine light — what it means
The amber engine outline (MIL / EML / check-engine light) means the engine computer has stored a fault — emissions, misfire, sensors, turbo, catalyst efficiency and more. Steady vs flashing is the critical split UK drivers need to know.
Also called: engine, check engine, MIL, EML
What it means
Emissions or engine control fault stored. Flashing often means misfire.
What to do first: Steady: book a scan soon. Flashing: stop when safe — catalytic converter risk.
Common causes
- Misfire, coil pack or spark plug faults (flashing = urgent)
- Lambda / O2 sensor or catalytic converter efficiency codes
- MAF/MAP sensor, boost leaks or EGR issues
- Loose fuel cap / EVAP leaks on some petrols
- DPF / AdBlue related codes on diesels that also set the MIL
Step-by-step
- 1Note whether the light is steady or flashing, and whether power, smoke or shaking changed.
- 2Flashing: stop when safe — continued misfire can melt a catalytic converter.
- 3Steady with normal driveability: book an OBD scan soon; do not keep clearing codes without fixing the cause.
- 4Photograph any message centre text — it helps the garage.
- 5After repair, confirm the light stays off through a proper drive cycle; an MOT can fail with the MIL on.
MOT note
A permanently illuminated MIL commonly fails the MOT emissions/electronic checks.
FAQs
- What does a flashing engine light mean?
- Usually an active misfire. Stop when safe and recover or limp very gently to a nearby garage — do not thrash the engine.
- Will a check engine light fail my MOT?
- Often yes if it stays on. Fix and verify before the test date.
Related
Other warning lights
Icons from Wikimedia Commons dashboard tell-tales / ISO 7000. Manufacturer artwork varies — your handbook wins.