@T5-T6-Schnappi Thanks for the advice. The error code I’m getting is P0420, related to the catalytic converter. My engine has recently undergone an overhaul, with the pistons replaced due to oil consumption. Since the rebuild, the engine doesn't behave like it used to— there’s a tingling sensation on the steering wheel, and it feels like I’m driving a diesel.

Besides the comfort issues, fuel consumption has increased to about 9.5L/100km (before the repair, I averaged 7.5L/100km). Now (20 000km after rebuild) I’m also getting errors related to the lambda sensors. I know that the mechanic unfortunately didn't assemble the engine according to the official Volvo procedure—they didn't use the required locking tools and just relied on timing marks. Therefore, I am certain the balance shafts are incorrectly installed, but I’m also worried about the timing and the VVT settings.

I also know that this car can be quite tolerant of certain issues... for instance, when I had a faulty PCV system, no error code appeared, even though the crankcase pressure was clearly compromised.