Red — stop now
Engine overheating
The coolant has overheated. What follows is a warped cylinder head — the most expensive repair that starts with a single lamp.
A red lamp means you should not keep driving. Pull over, switch the engine off and sort it out there.
What to do now
- Pull over and stop the engine. Turn the cabin heater to maximum on the way: it takes some heat away.
- Do not open the expansion tank cap on a hot engine — it holds boiling coolant under pressure.
- Let it cool for half an hour, then check the coolant level and look for leaks under the car.
Codes usually behind it
The lamp only says that something is wrong. The code says what exactly — read it with an adapter and look it up here.
P0217Engine overheatingP0128Coolant thermostat — temperature below regulating temperatureP0480Cooling fan 1 control circuit malfunctionP0691Cooling fan relay — low signal
What to read next
A lamp is not a diagnosis. The same symbol lights up for a dozen different reasons, and only the code stored in the car tells them apart.
How it feels behind the wheel
The same fault shows itself in different ways. Each sign below says what to look at in the live data.
The temperature gauge is climbingThe needle goes above its usual place, there is a hot smell from under the bonnet, and the heater may blow cold on a hot engine.Slow to warm up, the heater blows coldThe temperature needle sits low for ages, the cabin stays cold, and on the motorway it gets worse. Consumption rises noticeably.Smoke from the exhaustVisible smoke from the tailpipe. The colour is the clue: white, blue and black mean entirely different things.The cooling fan runs all the timeThe fan roars right after starting and does not stop even on a cold engine or in frost.
How the app helps
CarScan reads the codes behind the lamp through an OBD-II adapter, explains them in plain words and puts them into a report you can show to a mechanic.