Drivable — worth looking into
Fuel consumption has gone up
You refuel noticeably more often for the same driving. The lamp is usually off — the unit thinks it is coping.
There is no danger, but the symptom will not go away by itself: it is the early stage of something that gets pricier.
What to look at in the live data
- Fuel trims. Plus ten per cent or more means the unit is constantly adding beyond the calculation.
- Coolant temperature: if the engine never reaches operating temperature, the mixture stays rich all the time.
- The front oxygen sensor reading — is it still swinging or has it frozen.
- Air flow at 3000 rpm: it should rise five- or sixfold against idle.
Common causes, cheapest first
- Tyre pressure and extra load — free to check.
- A clogged air filter.
- The thermostat: the engine never warms up and runs rich all the time.
- A tired oxygen sensor — slow to respond.
- A mass air flow sensor reading low.
Codes that show up with this
P0128Coolant thermostat — temperature below regulating temperatureP0133Upstream O2 sensor slow response (bank 1) — usually a worn sensorP0171System too lean (bank 1) — air leak or not enough fuelP0101Mass air flow circuit range/performance
These parameters in the reference
Short term fuel trim B1Long term fuel trim B1Coolant temperatureO2 sensor B1S1 voltageMass air flow (MAF)Short term fuel trim B2Long term fuel trim B2Engine fuel rateO2 sensor B1S2 voltageCalculated engine loadAbsolute load value
Lamps that may be on
Do it step by step
Three readings separate a real fault from winter and traffic.Fuel use went up — where to start
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.