Avensis DPF Issue

I had similar symptoms with my old Renault Megane, though it was a petrol engine. It could indeed be the DPF. Have you checked for any sensor faults? Sometimes a faulty sensor can cause incorrect readings, leading to DPF issues. A vehicle inspection might be a good first step.

Sensor faults like which ones exactly? And inspection for what? Just back pressure?

Things like differential pressure sensors failing will cause incorrect readings and stop DPF regeneration. If it is clogged, regeneration (burning off the collected soot) is what clears it. An inspection should also check for exhaust leaks to make sure the car isn't working harder than usual.

Thanks. It was the DPF. Replacement cost me 1550€, but it runs fine now.