Sensor de nitrogênio-oxigênio FAW e conjunto lógico de sensor de alta temperatura: Por que estes 7 As peças críticas são essenciais para o controle de emissões

Bem-vindo a este guia técnico crítico sobre o Sensor de nitrogênio-oxigênio FAW e conjunto lógico de sensor de alta temperatura (Conjunto 551). This is the complete set of electronic “eyes and ears” for the emissions after-treatment system on the FAW Jiefang CA4251P66K24T1A3E5 6×4 trator semirreboque diesel.

O Sensor de nitrogênio-oxigênio FAW e conjunto lógico de sensor de alta temperatura é o “lógica” hub for the truck’s Selective Catalytic Reduction (Scr) sistema. Its components, the ‘Nitrogen-oxygen sensor assembly’ (3602510-51B) and the ‘High-temperature sensor assembly’ (3602505-51B-C00), provide the real-time data that the engine’s computer (ECU) needs to precisely manage the injection of Diesel Exhaust Fluid (DEF/Urea) and control emissions.

This in-depth guide is an essential resource for professional diesel technicians and parts specialists. Vamos desconstruir todo Sensor de nitrogênio-oxigênio FAW e conjunto lógico de sensor de alta temperatura em seu 7 componentes reparáveis, explaining the critical “lógica” of each sensor, their function in the SCR system, and the mounting brackets that protect them.

O “Lógica” of SCR: How This Assembly Works

O Sensor de nitrogênio-oxigênio FAW e conjunto lógico de sensor de alta temperatura é o “cérebro” of the modern emissions system. This system is known as **Selective Catalytic Reduction (Scr)**. Its sole purpose is to convert harmful Nitrogen Oxides (NOx)—a major component of smog and acid rain—into harmless nitrogen (N2) e água (H2O).

This chemical reaction is achieved by injecting Diesel Exhaust Fluid (DEF), a solution of urea and water, into the hot exhaust stream just before it enters a special catalyst (the SCR catalyst, parte da Assembleia 127).

This is where the “lógica” do Sensor de nitrogênio-oxigênio FAW e conjunto lógico de sensor de alta temperatura comes in. The truck’s Engine Control Unit (ECU) must know the *exact* amount of DEF to inject.

• **Inject Too Little:** If the ECU injects too little DEF, the chemical reaction will be incomplete. Harmful NOx will pass through the catalyst untreated, causing the truck to fail emissions standards and trigger a “Check Engine” light or “Limp Mode.”
• **Inject Too Much:** If the ECU injects too much DEF, it wastes expensive fluid and, more critically, causes “ammonia slip.” The excess urea doesn’t react and can crystallize (“cake”) inside the exhaust, criando uma enorme, concrete-like blockage that can destroy the SCR catalyst and even damage the engine.

O Sensor de nitrogênio-oxigênio FAW e conjunto lógico de sensor de alta temperatura provides the “closed-loop” feedback the ECU needs to inject the perfect, stoichiometric amount of DEF. It is the sensory input that makes this precise chemical reaction possible.

Componente principal 1: ‘Nitrogen-Oxygen Sensor Assembly’ (3602510-51B)

The ‘Nitrogen-oxygen sensor assembly’ (3602510-51B) is the most complex and critical part of the Sensor de nitrogênio-oxigênio FAW e conjunto lógico de sensor de alta temperatura. This is not a simple sensor; it is a sophisticated, multi-cell ceramic device with its own integrated control module.

**Função:** This sensor is typically installed *after* the SCR catalyst. Isso é “lógica” é ser o “report card” for the entire after-treatment system. It precisely measures the remaining parts-per-million (PPM) of Nitrogen Oxides (NOx) in the exhaust gas *after* it has been treated.

This sensor provides the final “feedback” in the closed-loop system. The ECU constantly monitors this sensor’s readings. If it detects that NOx levels are starting to creep up, it “knows” that its current DEF injection rate is insufficient, and it will precisely increase the injection “trim” until the sensor reports that NOx levels are back to near-zero.

**Falha:** The NOx sensor is a high-wear component in the Sensor de nitrogênio-oxigênio FAW e conjunto lógico de sensor de alta temperatura. It lives in an extremely hot, high-vibration environment and is sensitive to contamination from poor-quality fuel or DEF. A failed NOx sensor is a critical fault. The ECU loses its “olhos,” can no longer verify the emissions, and will immediately trigger a “Check Engine” luz, a “Limp Mode” (severe engine power reduction), and will log a fault for the emissions-control system. O Sensor de nitrogênio-oxigênio FAW e conjunto lógico de sensor de alta temperatura is completely disabled without this sensor.

Componente principal 2: ‘High-Temperature Sensor Assembly’ (3602505-51B-C00)

The ‘High-temperature sensor assembly’ (3602505-51B-C00) is the second “lógica” componente do Sensor de nitrogênio-oxigênio FAW e conjunto lógico de sensor de alta temperatura. This is a high-grade thermistor or thermocouple designed to withstand extreme exhaust temperatures (over 800°C).

**Função (SCR Logic):** The chemical reaction of DEF (urea) converting NOx is highly temperature-dependent. It only works efficiently within a specific temperature “window” (Por exemplo, 200°C to 450°C). O “lógica” of this sensor is to tell the ECU when it is safe to start injecting DEF. If the ECU injects DEF into a “frio” (below 200°C) sistema de exaustão, the urea will not convert to ammonia; it will simply crystallize, forming hard, white deposits (“caking”) that will block the SCR catalyst, a catastrophic and expensive failure. This sensor in the Sensor de nitrogênio-oxigênio FAW e conjunto lógico de sensor de alta temperatura prevents that.

**Função (DPF Logic):** This sensor also provides the critical “lógica” for **DPF Regeneration**. The Diesel Particulate Filter (DPF) traps soot, and it must be periodically cleaned out by “regenerating” (burning the soot at over 600°C). The ECU relies on this sensor to monitor the DPF’s temperature, garantindo um “regen” is both successful and safe (Ou seja,, it doesn’t get hot enough to melt the catalyst). This is a dual-purpose, essential component of the Sensor de nitrogênio-oxigênio FAW e conjunto lógico de sensor de alta temperatura.

The Mounting and Support System

The delicate electronic sensors in the Sensor de nitrogênio-oxigênio FAW e conjunto lógico de sensor de alta temperatura cannot simply be left to hang. They must be rigidly secured and their wiring protected from melting or chafing.

**’Nitrogen-oxygen sensor upper bracket’ (3602546-81C):** This bracket’s “lógica” is protection. The NOx sensor (3602510-51B) is a two-part device: o “sonda” that screws into the exhaust pipe, and a “control module” (a small black box) connected by a wire. This bracket is designed to mount the *control module* safely on the chassis frame, away from the extreme heat of the exhaust.

**’Main wiring harness bracket’ (3724426-68V):** This bracket is used to secure the main wiring harness for the Sensor de nitrogênio-oxigênio FAW e conjunto lógico de sensor de alta temperatura, preventing the wires from rubbing against the chassis (which would cause a short) or dangling near the hot exhaust pipe (which would melt them).

These brackets are secured with ‘Hex flange bolts’ (Q1840616) and ‘Hex flange nuts’ (CQ39606). O “mesa” design is a vibration-resistant logic that prevents the fasteners from loosening. Finalmente, the two ‘Plastic zip ties’ (T67417246) are a simple but critical part of the Sensor de nitrogênio-oxigênio FAW e conjunto lógico de sensor de alta temperatura, used to provide the final, secure fastening for the sensor wires.

FAW Nitrogen-Oxygen Sensor And High-Temperature Sensor Logic Assembly Parts List

A tabela a seguir fornece o completo, detalhamento de todos 7 components identified in the ‘Nitrogen-Oxygen Sensor And High-Temperature Sensor Logic Assembly’ (551) diagrama para o trator FAW CA4251P66K24T1A3E5.

Especificações Técnicas e Contexto de Montagem

As especificações para o Sensor de nitrogênio-oxigênio FAW e conjunto lógico de sensor de alta temperatura são definidos por sua função como “cérebro” of the emissions after-treatment system.