This Chevrolet Orlando diesel could not pass its roadworthiness inspection because of excessive smoke opacity. The initial reading was about 4.3; work at another garage brought it down to around 2.5, but the vehicle still failed. Work had previously been carried out on the injectors and intake-manifold flaps, but that was not enough to achieve the required result.

AutoChip read and checked the engine control unit software. The DPF and EGR functions had already been disabled, while no power increase had been made. After diagnosis, the software was adjusted and smoke opacity was checked again. The workshop recorded readings of 1.09 and 0.94; a later inspection recorded 0.49, and the vehicle passed.

A small amount of pale, slightly blue and darker smoke was still visible during the check. A passing smoke test alone does not prove that the engine has no mechanical faults. If smoke continues, a garage should investigate possible causes, including the injectors, turbocharger and crankcase ventilation. The video shows the software check and the measurement process.