Do not drive
The temperature gauge is climbing
The 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.
With this symptom you should not keep driving: the trip will cost more than a tow truck.
What to look at in the live data
- Coolant temperature as a number, not as a needle: on many cars the needle deliberately sticks in the middle of the scale and shows trouble last.
- Whether the fan comes on: with the car standing and the engine warm it must start by itself.
- Fan relay and temperature sensor codes.
- Fuel trims: overheating often comes alongside a lean mixture.
Common causes, cheapest first
- Low coolant or air in the system — free to check and checked first.
- The fan does not come on: the relay or the fuse.
- A thermostat stuck closed.
- The water pump or a blocked radiator — that one goes to a mechanic.
Codes that show up with this
P0217Engine overheatingP0480Cooling fan 1 control circuit malfunctionP0691Cooling fan relay — low signalP0118Engine coolant temperature circuit high input
These parameters in the reference
Coolant temperatureShort term fuel trim B1Engine oil temperatureAmbient air temperatureCommanded EGREGR error
Lamps that may be on
Do it step by step
P0171 is not a random string but an address. We take it apart, sign by sign.Reading a fault code: the letter and four digits
A symptom is not a diagnosis. The same sign comes from a dozen different causes — the readings are what tell them apart, not the feeling.
How the app helps
CarScan shows exactly these readings live, remembers the highest and the lowest value of the trip, and puts them into a report you can hand to a mechanic.