Even after changing the middle exhaust pipe, the fault light is still on. What could be the reason?

Is the inside of the V40 exhaust pipe black, like soot? Could it be too much carbon buildup?

Even after changing the middle exhaust pipe, the fault light is still on. What could be the reason?

What could be the reason for the headlights and brake lights turning on by themselves at night?

The 2008 Volkswagen Touran 1.8T shows a fuel consumption of 11 liters on the highway. After changing the fuel injectors and spark plugs, there's still no improvement. What could be the reason?

The dashboard reported low transmission performance, and then the car wouldn't accelerate. After restarting, the warning light went off and it drove normally. What could be the reason? (The onboard computer cleared the fault light, but it came back on before I got home.)

The 2014 model with a 3.5L engine shows the engine warning light and exhaust system fault light at 100,000 km. The sensors have been replaced, but after a while, the lights come on again. Does anyone know what the reason might be? Generally, the lights only come on when driving at high speeds. Could it be related to the Evans waterless coolant that was changed a few years ago at the 4S shop?

Engine shows fault code, acceleration is weak, what could be the reason?

When the fuel gauge still shows three bars short after filling up the tank until the pump stops, what could be the reason?

This pipe seems to be leaking oil. Does this happen to you as well? Also, what is the purpose of this pipe? Is it for exhaust gas recirculation?

The engine won't start, and the EPC, battery, and engine fault lights on the dashboard are all on. What could be the reason?