Check engine lights are sometimes accompanied by noises, smells, and vibrations that can help diagnose the underlying issue. But sometimes, that annoying little light comes on with no other indication ...
Smelling gas when the AC is on usually means raw fuel or exhaust fumes are being drawn into the cabin via the ventilation ...
Smelling petrol when the AC is on usually means raw fuel or exhaust fumes are being drawn into the cabin via the ventila ...