0444043087 | Genuine Volvo® DEF Doser Injector Unit D11, D13

VNL (2007–2024)
VNR (2018–2024)
VNM, VNX, VHD

Mack trucks

Also used across some other heavy trucks due to cross-compatibility:

Freightliner Cascadia / Columbia (some years)
Kenworth T660, T680, T800, W900
International ProStar

It’s especially common on Volvo D11 / D13 engines (roughly 2008–2016 and newer variants).

When DEF is sprayed into hot exhaust:

• DEF converts into ammonia

• The ammonia reacts in the SCR catalyst

• Harmful NOx (nitrogen oxides) are converted into nitrogen + water

This is how diesel vehicles meet emissions laws.

3. Controlled by the ECM/PCM

The engine computer decides:

• When to spray

• How much to spray

• Spray timing based on exhaust temperature & load

A failing doser can cause:

• DEF system warning light

• Check Engine Light

• Low or no NOx reduction

• Crystallized DEF buildup at the injector

• Poor fuel economy

• Reduced engine power (“limp mode”)

• Smell of ammonia in exhaust

• DEF consumption too high or too low

Common trouble codes:

• P20E8 (low DEF pressure)

• P204F (SCR system)

• P20EE (NOx efficiency below threshold)

• P2033/P2032 (temperature issues affecting DEF spray)