Форсунка системы нейтрализации пропускает

The exhaust-side fuel injector passing fuel when it should be closed. It is the more damaging of that injector's two failure modes — a coked one delivers too little and merely prevents regeneration, while a leaking one adds fuel nobody commanded to a very hot exhaust.

Uncommanded fuel in the exhaust raises temperatures unpredictably. The result is exhaust over-temperature codes, thermal damage to the filter or catalyst, and in the worst case a fire risk in the aftertreatment — which is why the module treats it seriously and will inhibit regeneration entirely.

Its signature is exhaust temperature that rises when no regeneration is running. That is the observation to make, because a leaking and a coked injector both produce performance codes and the temperature trace separates them immediately. Fuel pooling in the exhaust after shutdown is the other evidence. Check the shutoff valve upstream too — a valve that does not seal produces the identical symptom with a sound injector.