Injektor der Abgasnachbehandlung defekt

The injector that sprays fuel into the exhaust stream to raise temperature for a particulate filter regeneration — a seventh injector on the exhaust side, not one of the cylinder injectors. Naming it precisely matters because the code reads like an engine fuelling fault and is not one, and a diagnosis that starts at the rail is starting in the wrong place.

Its position is what destroys it. It sits in the exhaust with combustion products flowing past its tip, so it cokes. A coked injector delivers a distorted or restricted spray, so regeneration temperatures are not reached, and the module reports its performance rather than its condition. A leaking one is worse — fuel entering the exhaust when none was commanded raises temperatures unpredictably and can be enough to damage the filter it exists to protect.

Distinguish the circuit codes from the performance codes before acting. Open, low and high name the wiring and the driver, and are answered with a meter. Performance and stuck-open codes name the injector body. Check for coking at the tip before fitting a new part, and be aware that a new injector into an exhaust system that coked the last one will coke as well unless what caused the excess soot is found.