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Red lights require you to stop as soon as possible, yellow ones signal a fault to be checked soon, green and blue ones simply indicate active functions. The colour is the first useful clue to how serious it is.

Red lights: stop

• Oil pressure: immediate stop, risk of seizure
• Engine temperature: risk to the head gasket
• Battery: the car is not charging, limited range
• Brakes: possible leak in the circuit
• Airbag: passive safety not guaranteed

Yellow lights: check soon

• Engine (check engine) light, steady or flashing
• ABS, ESP, TPMS, DPF/FAP, AdBlue
• Flashing preheat light on diesels

Rule of thumb

A flashing yellow light is more serious than the same light steady: a flashing engine light, for example, indicates a misfire that can ruin the catalytic converter. In that case reduce speed and have the car checked immediately.

How MasterTuning helps

We read the ECU with professional tools, interpret the real fault codes and tell you what really needs repairing, without unnecessary replacements. Diagnosis, repair and software recalibration at our centres throughout Italy.

Read more: vehicle database · find an installer · what is ECU remapping

Is a warning light on? Contact us for a diagnosis or find your nearest MasterTuning centre.

Frequently asked questions

Which car warning lights require you to stop?

The red oil pressure and engine temperature lights require an immediate stop; battery and brakes also require you to stop as soon as possible.

Is a yellow engine light serious?

If it is steady you can reach the workshop driving carefully; if it flashes, reduce speed immediately because the catalytic converter can be damaged.

Do green and blue lights signal faults?

No, they indicate active functions such as lights, high beam or cruise control.