Capteur de température de vapeurs de carburant défectueux

The sensor measuring the temperature of fuel vapour in the evaporative system, which is a different device from the fuel temperature sensor in the tank or rail. Confusing the two sends the diagnosis to the wrong part of the vehicle, and their names are close enough that it happens.

Its purpose is to make leak testing valid. A sealed tank's pressure changes with temperature alone, so the module must know the vapour temperature to decide whether a pressure change indicates a leak or simply the sun coming out. Without a trustworthy reading it cannot run the test, so the practical consequence is usually a monitor that never completes rather than a driveability fault — which matters at an emissions inspection.

A wrong reading is worse than a missing one, because it lets the test run and produces a verdict nobody should trust: a false leak on a sound tank, or a genuine leak masked. Compare it against ambient after an overnight soak — vapour temperature and air temperature should agree closely on a cold vehicle, and a sensor that disagrees there has an offset fault no circuit test will reveal.