Diesel Engine Auto Nox Sensor Replacement Cummins 2894941 3687334 3687334RX

The 5WK96673A is a high-precision, planar dual-cell limiting current type nitrogen oxide (NOx) sensor, designed for 12V medium-duty and heavy-duty diesel engine exhaust aftertreatment systems. This electrochemical sensor continuously monitors the concentration of nitrogen oxides (NOx) in the exhaust stream and communicates with the Engine Control Unit (ECU) via digital CAN bus (SAE J1939) protocol. This real-time feedback allows for precise control of the Selective Catalytic Reduction (SCR) system, ensuring compliance with stringent emission standards such as EPA10, Euro V, Euro VI, and others.

The sensor integrates a zirconium dioxide (ZrO₂) ceramic sensing element with an electronic control unit into a single, robust unit that is installed directly in the exhaust system. It is designed to meet the demands of heavy-duty applications, providing long service life and reliable operation.

The 5WK96673A NOx sensor is a direct replacement for a number of original equipment (OE) part numbers. When searching for a new sensor, it is crucial to verify the part numbers match, as using the wrong part will lead to communication errors and system failure. Always match the Continental reference number (5WK96673A) to ensure correct functionality.

⚠️ Important: Confirm your original sensor‘s OE part number on the back of the old unit. If uncertain, rely on the Continental number 5WK96673A for the most accurate fit. This is true for all forms of this part, including 5WK96673A OEM, 5WK96673A CUM, and the standard 5WK96673A.

The 5WK96673A is specifically engineered for 12V diesel engines and is most commonly associated with Cummins engine platforms. It is frequently used as a System Outlet (downstream) sensor, installed after the SCR catalyst, to verify emissions compliance.

• Cummins ISX: 11.9L to 15L heavy-duty engines (e.g., ISX15 14.9L). This sensor is a known replacement for the upstream engine outlet on a 2011 Peterbilt 387 with a Cummins ISX 15.0L engine.

• Cummins ISB / ISBe / ISC / ISL: 6.7L, 8.3L, and 8.9L platforms commonly found in medium-duty trucks and buses.

• Cummins QSB / QSL: Industrial and off-highway applications.

• Other Engines: Some compatibility with Ford 6.7L Power Stroke diesel engines (model years 2011-2016).

This sensor is compatible with a wide range of commercial vehicles, predominantly those powered by Cummins engines, including but not limited to:

⚠️ Note: Before purchase, always verify your specific vehicle's engine and model year to ensure cross-references match the original sensor’s specifications.

A failing or contaminated 5WK96673A NOx sensor will manifest various drivability and performance issues. Early diagnosis and replacement can prevent costly damage to other exhaust aftertreatment components like the SCR catalyst and DEF injector.

• Reduced Engine Performance / Limp Mode: The vehicle may go into a “limp” or derate mode to prevent emissions violations, resulting in a dramatic loss of power and restricted speed.

• Illuminated Warning Lamps: The malfunction indicator lamp (MIL) or check engine light will illuminate on the dashboard. An illuminated SCR or engine warning lamp is a clear sign.

• Increased Fuel Consumption: The ECU may compensate for inaccurate NOx data by altering the fuel/air mixture, leading to a noticeable drop in fuel efficiency.

• Poor Engine Starting / Cold Start Problems: You may experience rough idling, engine hesitation, or difficulty starting when the engine is cold.

• Excessive DEF Consumption or System Failure: A faulty sensor can send incorrect signals to the ECU, causing the SCR system to over-inject Diesel Exhaust Fluid (DEF) or causing the SCR system to stop injecting DEF altogether.

• Failed Emissions Test: The vehicle will likely fail a state-mandated emissions inspection due to the inability of the SCR system to properly reduce tailpipe NOx.

• Associated Diagnostic Trouble Codes (DTCs):

  • P2200: NOx Sensor Circuit / Open (Bank 1)

  • P2201: NOx Sensor Circuit Range/Performance (Bank 1)

  • P229F: NOx Sensor Circuit Intermittent/Erratic

  • P229E: NOx Sensor Circuit Signal Plausibility Failure

  • U05A2: Erroneous Signal (Dew point reached with ignition off / timeout)

  • P225C / P225D: NOx Sensor 1/1 Performance, Signal Stuck High/Low

  • P20EE: SCR NOx Catalyst Efficiency Below Threshold

💡 Tip: If you are experiencing a combination of these warning lights and performance issues, it is highly recommended to have your system’s fault codes read with a diagnostic scanner to pinpoint the exact faulty component(s) before purchasing a replacement.

Selecting the correct NOx sensor is critical for restoring engine performance and ensuring emissions compliance. Consider these crucial factors before buying a 5WK96673A:

The most common mistake is mismatching part numbers. The Continental 5WK96673A is the primary reference. Always check your old sensor. The connector is a flat 4-pin (or square 4-pin) type. The 5WK96673A is a 12V sensor and must not be confused with 24V variants.

This is a 12V sensor. Before installation, verify your vehicle’s electrical system is 12V. Using a 12V sensor on a 24V system will cause immediate and permanent damage. Contamination from poor DEF quality, oil leaks, or SCR catalyst failure is a leading cause of NOx sensor failure. Replacing the sensor without addressing the root cause will lead to rapid failure again.

Quality varies significantly. A low-priced sensor may lack proper calibration or durability. Look for suppliers with clear quality certifications. Consider suppliers offering a strong 12-month/unlimited mileage warranty. Some premium sensors now feature "Generation 2" software with “re-flashing” technology to ensure compatibility with future OEM software updates, providing a more future-proof solution.

Proper installation is key. The sensor is typically installed using a thread size of M20 x 1.5. Do not touch the ceramic sensing tip with bare hands. Use the supplied new crush washer and torque to the manufacturer‘s specifications (approx. 40-60 Nm) to avoid exhaust leaks.

It is imperative to have the vehicle’s computer reprogrammed. Replacing the sensor physically is only half the job. A diagnostic tool must be used to clear all existing DTCs and perform a NOx sensor replacement adaptation or teach-in procedure. This allows the ECU to learn the new sensor’s baseline values. Failure to do so will often result in persistent fault codes even with a brand-new sensor. If you are not comfortable with this procedure, professional installation is strongly recommended.

Product Summary

The 5WK96673A is a critical 12V NOx sensor for modern diesel engines, ensuring the SCR system can accurately reduce harmful emissions. It is a known replacement for several OE part numbers, including 2894941 and 5WK96755A. By adhering to proper selection, careful installation, and mandatory ECU adaptation, you can restore your vehicle’s performance, fuel economy, and full emissions compliance.