Steady or flashing?
Steady light. A fault has been detected that should be checked soon. The car may feel completely normal.
Flashing light. Usually a serious engine misfire. Unburnt fuel can overheat and damage the catalytic converter. Reduce speed, avoid hard acceleration and have the vehicle checked as soon as possible.
Light plus other warnings (oil pressure, temperature, battery) or the car going into reduced-power “limp mode”: pull over safely and get advice before driving further.
Common causes
- Ignition problems — worn spark plugs or a failing ignition coil causing misfires
- Sensor faults — oxygen sensors, the mass airflow sensor, or coolant or crankshaft sensors
- Fuel system issues — a loose or faulty fuel cap, injector problems, or incorrect fuel mixture
- Emissions components — the catalytic converter, EGR valve, or on diesels the diesel particulate filter (DPF)
- Vacuum or air leaks in intake hoses and gaskets
- Wiring and connector faults, including damage from heat, water or rodents
What you can do
- Note whether the light is steady or flashing, and when it came on.
- Notice any changes: rough running, loss of power, higher fuel consumption, smells or noises.
- If you recently refuelled, check that the fuel cap is closed properly.
- Avoid ignoring it — a small fault left too long can cause wider damage.
How we diagnose it
We connect a diagnostic scan tool to read the stored and pending codes and review live data from the engine’s sensors. The technician then tests the suspected components and wiring to confirm the cause, and explains the findings with an estimate before any repair. After the repair, codes are cleared and the system re-checked.
