2010 Prius II with 201,600 miles and an intermittent P0401 code

P0401 Exhaust Gas Recirculation Flow Insufficient Detected
The problem is with the EGR and you need to solve it.
On this generation, the EGR gets clogged over time and needs to be cleaned.
In addition, there may be ongoing problems that escalate.
Engine overheating, gasket failure, coolant leakage into the cylinders, uneven engine operation and, finally, engine seizure.

 

Has all of the first paragraph work been done then? If so, and if done properly, you “may” be ok for some time. Barring brake booster or hybrid battery failures.

you should reclean the EGR every 50k miles. My 2 cents: failure to do this is why the head gasket failed. And Toyota is keeping quiet.

 

This is exactly why we opted to get out of a 13 Persona and a 2010 JBL solar roof car You personally have to reach the point where things start making sense or maybe you never do We need both types in the world unfortunately so there's always that. All of these types of people keep the industry going around and round this styles of thinking are or can be personal choices

 

Sometimes a quick inspection of the rotor in the EGR valve will show a rut worn through the ski-jump rotation stop inside it. That can also give you a recurring P0401, even after you've eliminated clogging as a cause.

 

Thought's crossed my mind a few times: could a carbon-clogged EGR system make the valve work more, be more prone to dig that rut?