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Engine NOx Sensor

Car NOx Sensor

Nitrogen Oxide NOx Sensor

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Urea Doser Pump

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Crankshaft Position Sensor

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Company news about What does a DEF injector do?

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What does a DEF injector do?

2026-04-17

The DEF Injector (Diesel Exhaust Fluid Injector) is a critical component within the Selective Catalytic Reduction (SCR) system of diesel vehicles. It is responsible for precisely injecting a urea solution—known as DEF (or commonly referred to as "automotive-grade urea")—into the exhaust pipe. Here, it undergoes a chemical reaction with the nitrogen oxides (NOx) present in the exhaust gases, converting them into harmless nitrogen gas and water vapor, thereby significantly reducing harmful emissions.

This process is vital for meeting the stringent emission standards required of modern diesel engines. The specific operating principle is as follows:

As exhaust gases exit the engine, the DEF injector releases DEF—in a finely atomized form—into the high-temperature exhaust stream at a precisely timed moment.
Under high temperatures, the DEF decomposes into ammonia (NH₃), which then enters the catalytic converter.
Within the converter, the ammonia reacts with the NOx in the presence of a catalyst to produce nitrogen (N₂) and water (H₂O), thereby achieving emission purification.
If the DEF injector becomes clogged, develops a leak, or suffers a control malfunction, the following issues may arise:

Emission levels exceeding regulatory limits, resulting in a failure to pass annual vehicle inspections.
The engine entering a "limp mode" (reduced power mode), thereby compromising driving performance.
Illumination of the "SCR System Fault" or "Check Engine" warning lights on the dashboard.
Consequently, ensuring the proper functioning of the DEF injector is not merely a matter of environmental compliance; it also directly impacts the vehicle's overall reliability and the user's driving experience.

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Home > News >

Company news about-What does a DEF injector do?

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What does a DEF injector do?

2026-04-17

The DEF Injector (Diesel Exhaust Fluid Injector) is a critical component within the Selective Catalytic Reduction (SCR) system of diesel vehicles. It is responsible for precisely injecting a urea solution—known as DEF (or commonly referred to as "automotive-grade urea")—into the exhaust pipe. Here, it undergoes a chemical reaction with the nitrogen oxides (NOx) present in the exhaust gases, converting them into harmless nitrogen gas and water vapor, thereby significantly reducing harmful emissions.

This process is vital for meeting the stringent emission standards required of modern diesel engines. The specific operating principle is as follows:

As exhaust gases exit the engine, the DEF injector releases DEF—in a finely atomized form—into the high-temperature exhaust stream at a precisely timed moment.
Under high temperatures, the DEF decomposes into ammonia (NH₃), which then enters the catalytic converter.
Within the converter, the ammonia reacts with the NOx in the presence of a catalyst to produce nitrogen (N₂) and water (H₂O), thereby achieving emission purification.
If the DEF injector becomes clogged, develops a leak, or suffers a control malfunction, the following issues may arise:

Emission levels exceeding regulatory limits, resulting in a failure to pass annual vehicle inspections.
The engine entering a "limp mode" (reduced power mode), thereby compromising driving performance.
Illumination of the "SCR System Fault" or "Check Engine" warning lights on the dashboard.
Consequently, ensuring the proper functioning of the DEF injector is not merely a matter of environmental compliance; it also directly impacts the vehicle's overall reliability and the user's driving experience.

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