Exhaust Aftertreatment Fuel Injector

Sprays a metered amount of diesel directly into the exhaust, upstream of the oxidation catalyst, so that burning it there raises the temperature entering the particulate filter enough for a regeneration to complete. Often called the seventh injector or the dosing injector.

It exists to keep fuel out of the engine. The usual way to raise exhaust temperature is a late post-injection inside the cylinder, and its well-known cost is that some of that fuel lands on the cylinder wall and is scraped into the sump — oil level rising, oil diluted with diesel, and its ability to protect bearings falling away. A vehicle fitted with an exhaust injector is one whose oil is being protected from that.

It is not a reductant injector. That sprays urea solution for oxides of nitrogen and belongs to a different system; the names are close enough to confuse and the parts do not interchange.

Two failures, with very different urgency. Coking is the ordinary one — it sprays into the dirtiest place on the vehicle, so carbon builds on the nozzle until the spray collapses and regenerations stop completing; on many vehicles the tip and seal are serviceable separately and much cheaper than the injector. Leaking is the serious one: a nozzle that no longer seals passes raw fuel continuously into a hot exhaust, which can drive the filter far beyond its controlled regeneration temperature and crack or melt the substrate — and an uncontrolled exothermic reaction under a vehicle is a fire risk. A strong smell of unburnt diesel from the exhaust or unusual heat underneath is a reason to stop.

Also known as: seventh injector, 7th injector, dosing injector, hc injector, hydrocarbon injector, dpf dosing injector, exhaust fuel injector, regeneration injector

Referenced by 42 codes

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Codes involving this component (42)

Other components in Exhaust and Emissions

Information, not instruction

CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.

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