Do not drive
It stalls while driving
The engine dies while the car is moving — at speed, in a corner or when lifting off. The steering and brakes go heavy at once.
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
- Stored codes right after the stall: a crankshaft sensor code is the most common answer here.
- Engine speed at the moment it died, if the app managed to record it: an abrupt drop to zero and a slow fade mean different things.
- System voltage: a weak alternator drags the supply down and the unit loses control.
- Fuel pressure, if the car reports it.
Common causes, cheapest first
- The crankshaft position sensor — a classic sudden death without warning.
- A bad earth or connector: an open circuit over a bump gives exactly this picture.
- A weak fuel pump or clogged filter — it dies under load and starts again a minute later.
- The alternator: the dashboard dims first, then everything switches off.
Codes that show up with this
P0335Crankshaft position sensor circuit malfunctionP0230Fuel pump primary circuit — malfunctionP0562System voltage lowP0620Generator control circuit — malfunction
These parameters in the reference
Engine RPMControl module voltageCoolant temperatureFuel pressureFuel rail pressureCalculated engine loadAbsolute manifold pressure
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.