Final answer:
The function of a seventh injector in a six-cylinder engine is to dose diesel fuel for DPF regeneration. This injector helps raise the temperature to allow the DPF to burn off accumulated particles.
Step-by-step explanation:
The function of a seventh injector in a six-cylinder engine is to dose diesel fuel for DPF regeneration.
The DPF (Diesel Particulate Filter) is an emissions control device that captures and stores particulate matter from the engine's exhaust.
Over time, the DPF becomes saturated with soot and needs to be regenerated to burn off the accumulated particles. The seventh injector injects an additional amount of diesel fuel into the exhaust system during regeneration, raising the temperature and allowing the DPF to clean itself.