Commercial Electrochemical Aftermarket NOx Sensor YSZ Ceramic 2871978 A029E786

The 5WK96674 (also commonly referenced as 5WK96674A) is a planar dual-cell limiting current type nitrogen oxide (NOx) sensor designed for 12V diesel engine exhaust aftertreatment systems equipped with Selective Catalytic Reduction (SCR). It is an electrochemical sensor that continuously monitors the concentration of nitrogen oxides and oxygen in the exhaust stream and communicates with the Engine Control Unit (ECU) via digital CAN bus protocol. This real-time feedback enables precise control of the SCR system and ensures compliance with EPA 2010, Euro V, Euro VI, and equivalent emission standards.

The sensor consists of a ceramic sensing element and an integrated electronic control unit, forming a single unit installed in the exhaust system. The ECM uses the NOx information to monitor and adjust the amount of Diesel Exhaust Fluid (DEF) injected into the exhaust stream, optimizing NOx reduction and maintaining regulatory compliance.

The NOx sensor transmits the NOx value in the exhaust gas to the ECU in real time after normal operation. The ECU does not merely judge whether the exhaust gas is qualified by monitoring the real-time NOx value; rather, it detects whether the NOx value in the exhaust gas exceeds the standard through a set of NOx monitoring programs. The upstream sensor is used for the aforementioned feedback loop, while the downstream sensor is used mainly to confirm that legislated emissions limits have not been exceeded.

Most engines equipped with SCR aftertreatment systems utilize two NOx sensors:

• Upstream sensor (pre-SCR) – installed before the SCR catalyst, providing real-time feedback to precisely meter DEF injection

• Downstream sensor (post-SCR / outlet) – installed after the SCR catalyst to confirm that emissions limits have not been exceeded

The 5WK96674 / 5WK96674A is typically designated as an Outlet / Downstream NOx sensor.

Important: The 5WK96674 / 5WK96674A operates on a 12V system voltage. Do not install on 24V systems. Always verify your vehicle‘s electrical system voltage before purchase.

The following part numbers are directly interchangeable with 5WK96674 and 5WK96674A. When searching for a replacement, these numbers may appear on the original sensor label, in supplier catalogs, or in vehicle manufacturer documentation. Always verify physical connector type, cable length, voltage rating, and thread size before purchasing.

From multiple supplier sources, the following cross-references have been verified:

• The sensor has direct cross-reference numbers: 2871978, 904-6004, 4984053, 4984576, 2894939, A034X846.

• A supplier cross-reference list includes: 5WK96674A, NOX-CXX-014, 1831900, 2871978, 2894939, 2894939RX, 4984053, 4984576, 5462435, 6398823R.

• A listing shows replacement part numbers: 2871978, 2894939, 5WK9 6674A, 5WK96674A.

• The sensor is also referenced as 5WK96674A, 5WK96674, 2894939.

⚠️ Important: The underlying part number (5WK96674 / 5WK96674A) is the most reliable way to ensure correct functionality. OEM cross-reference numbers are for identification purposes only. Always verify against your original sensor’s label before purchasing. Different suffixes may indicate minor production revisions or calibration differences. Match the full alphanumeric string on your original sensor whenever possible.

The 5WK96674 / 5WK96674A NOx sensor is designed for 12V commercial vehicle electrical systems and is primarily used with Cummins diesel engines in medium-duty and heavy-duty applications meeting EPA 2010 emission standards.

This sensor is primarily associated with Cummins diesel engines in commercial vehicle, truck, and bus applications. The sensor is designed to work with engines equipped with SCR aftertreatment systems and is typically installed as an outlet (downstream) NOx sensor.

Based on cross-reference information and supplier listings, the 5WK96674 / 5WK96674A is compatible with the following engine platforms:

Specific application: The 5WK96674A is listed as compatible with Cummins ISB 6.7L (2010–2012 model years) and Cummins ISX 15L (2010–2012 model years) as an outlet (downstream) sensor.

The 5WK96674 / 5WK96674A sensor is compatible with a wide range of commercial vehicles equipped with Cummins diesel engines:

Source: Application listing includes FE 2011–2012, RE 2011–2012, Vision School Bus 2011–2012, Capacity TJ5000/TJ6500 2011–2012, Capacity TJ9000 2011, 108SD 2012, Argosy 2012, B2 2011–2012, Cascadia 2011–2012, Columbia 2012, FLD132 2011, M2 106 2011–2012, MB Line 2011–2012.

The 5WK96674 / 5WK96674A is designed for vehicles meeting:

• EPA 2010 (EPA10) – North American heavy-duty emissions standards (primary application)

• Euro V / Euro VI – European emissions standards

• Equivalent Tier standards for off-road equipment

• The sensor meets EPA and EU emissions standards, ensuring legal operation across regulated markets

The 5WK96674 / 5WK96674A is typically specified as an Outlet NOx Sensor (downstream of the SCR catalyst). The downstream sensor is used mainly to confirm that legislated emissions limits have not been exceeded. Always verify the correct position on your vehicle before installation, as some platforms use two NOx sensors (upstream and downstream) while others may use only one.

Due to the diversity of commercial vehicle configurations, physical fitment alone does not guarantee proper function. To confirm compatibility:

1. Check your original sensor label – Match the full part number 5WK96674 or 5WK96674A (located on the back of the old unit)

2. Verify voltage – The 5WK96674 / 5WK96674A is a 12V sensor; confirm your vehicle electrical system is 12V

3. Count connector pins – Black flat 4-pin sealed connector type (some sources specify “Black Flat 4 plug”)

4. Measure cable length – Approximately 590–795 mm (verify against original)

5. Confirm thread size – M20 x 1.5

6. Verify mounting position – Typically Outlet / Downstream sensor; confirm with original sensor location

7. Verify vehicle model year – This sensor is typically used for vehicles from model years approximately 2010 through 2012, though compatibility may extend to other years

⚠️ Important note: Compatibility extends beyond physical fitment. The sensor must match the ECU’s CAN communication protocol. Always reference your original sensor‘s part number or consult vehicle-specific documentation before purchasing. For urgent or breakdown orders, suppliers may offer emergency service channels for critical replacement needs.

A degraded or failed 5WK96674 / 5WK96674A NOx sensor will typically trigger one or more of the following symptoms. Early recognition can prevent secondary damage to the SCR catalyst, DEF injector, Diesel Exhaust Fluid system, or Diesel Particulate Filter.

The most common first indicator is the illumination of the check engine light on your dashboard. The ECU detects abnormal readings—or stops sending data entirely—and logs a diagnostic trouble code (DTC). Common symptoms include an illuminated check engine light and emission system-related error codes.

Common codes associated with NOx sensor failure include:

The rationality check for this sensor consists of sensor stuck low and stuck high checks, performed whenever the engine operates under highly transient conditions. A fault condition is reached whenever the NOx sensor values are below or above a fault limit.

When the NOx sensor provides faulty readings, the ECU enters a default or “limp” mode to protect the engine and emission system. In this state, fuel and air delivery may be restricted, leading to noticeable power loss, sluggish acceleration, and poor throttle response. Reduced engine performance or fuel efficiency is a common symptom.

A malfunctioning NOx sensor sends inaccurate data to the ECU, which in turn may adjust the air-fuel mixture incorrectly. This imbalance often causes the engine to inject more fuel than necessary, leading to increased fuel consumption. Decreased fuel efficiency and poor engine performance are common symptoms of a faulty NOx sensor.

A faulty NOx sensor disrupts the ECU and SCR, triggering fault codes and leading to incorrect DEF dosing. False high NOx readings can cause the SCR to over-dose DEF, resulting in rapid DEF (AdBlue) depletion and potential crystallized injector. Increased emissions or failed emission tests may also be observed.

Since the NOx sensor directly impacts your vehicle‘s emissions, a failure can cause your vehicle to exceed acceptable limits, resulting in a failed test.

When the NOx sensor is unable to maintain a reliable output, its signal quality will be set to “not reliable.” This can occur during fast transients and fast variations in NOx sensor measurement value. Too long a duration of unreliable sensor signal quality is considered an error, and the OBD monitor is designed to detect faulty startup behavior.

A malfunctioning NOx sensor can disrupt the SCR process, leading to improper DEF dosing. This may produce a strong ammonia or sulfur smell from the exhaust, indicating that the emissions control system is not functioning correctly.

If the internal heater fails (open circuit), the sensor never reaches operating temperature, and DTCs set immediately after cold start. The heater circuit is critical for bringing the sensing element to operational temperature quickly after engine startup.

Before replacing the 5WK96674 / 5WK96674A, perform these basic checks:

1. Visual inspection – Look for damaged cable insulation, chafing against chassis components, bent pins, or a melted/cracked connector

2. Check DTC status – Using a diagnostic scan tool, verify which codes are present and whether they are active or intermittent. Look for codes such as P225C (signal stuck high) or P225D (signal stuck low).

3. Heater resistance test – Measure between heater positive and heater ground pins using a multimeter. An open circuit or short indicates internal failure

4. Voltage supply – With key on and engine off, verify 12V power at the sensor connector

5. CAN bus integrity – Check CAN High and CAN Low lines for proper termination

6. Live data review – Observe NOx readings; a fixed reading of 0 ppm or pegged at maximum without change points strongly suggests a faulty sensor

Note: A recurring NOx sensor code may also be caused by an exhaust leak upstream of the sensor, poor DEF quality, a failed DEF injector, or a contaminated SCR catalyst. Perform a thorough system diagnosis before sensor replacement to avoid repeat failures. When the NOx sensor is unable to maintain a reliable output, its signal quality will be set to “not reliable,” which may indicate internal sensor issues.

Purchasing the correct 5WK96674 / 5WK96674A NOx sensor and installing it properly is essential for reliable SCR performance and avoiding costly mistakes. Commercial vehicle operators should pay special attention to voltage compatibility, sensor position, and installation procedures.

• Match the full printed number on your original sensor – 5WK96674 or 5WK96674A (the “A” suffix is most common and indicates a production revision)

• Match OEM cross-references – Verify compatibility with numbers such as 2894939, 2871978, 4984053, 4984576, 904-6004, A034X846, and 5462439

• Confirm “Outlet” designation – This sensor is typically used as a downstream (outlet) sensor, not an upstream sensor

• Avoid “universal fit” listings – The 5WK96674 / 5WK96674A is a specific digital device; generic sensors are unlikely to communicate correctly with your ECU

• Always ensure the replacement sensor matches the original part numbers for compatibility

• Reputable supplier – Choose a supplier with documented quality control and a minimum 6–12 month warranty. Some suppliers offer a 12-month warranty

• Avoid used or “remanufactured” – NOx sensors degrade internally from heat and contamination. Used sensors almost always fail prematurely. Look for 100% new products

• Price guideline – Authentic quality replacements typically range from approximately $100 to $260:

  • Economy/aftermarket: $100–150

  • Premium aftermarket: $170–260

  • Suspiciously low prices (below $80) may indicate counterfeit or defective products

• Packaging – New sensors should be shipped in protective packaging with a protective cap over the ceramic tip

• Third-party testing – Look for sensors that have been tested and accredited by third parties to ensure reliable emission control and cost-effective DEF consumption

• Future-proof capability – Some replacement sensors feature future-proof software re-flashing technology to ensure compatibility with OE software updates

• Do not touch the ceramic sensing tip – Skin oils cause thermal shock cracking during the first heat-up cycle

• Inspect cable routing – Ensure the new cable follows the original path, using existing clips and standoffs. Avoid sharp bends or contact with moving parts

• Remove protective cap only when ready – Keep the sensor clean by removing the protective cap immediately before installation. Do not allow any dirt to contaminate the lubricated threads, and do not wipe anti-wear agent from the thread surface.

• Clean the bung threads – Use a thread chaser (M20 x 1.5) to remove carbon buildup and rust before installation

• Use clean, dry tools – Do not install the sensor if mechanical damage is found. Always use clean, dry tools for installation.

• Inspect electrical connections – Check the vehicle-side connector for cleanliness, corrosion, and sealing integrity before installing the new sensor

Follow this sequence for proper installation:

1. Safety First – Disconnect the vehicle’s battery to prevent electrical hazards

2. Secure the ECU unit – Use screws to mount the sensor’s electronic control unit to the vehicle. Determine the appropriate torque based on screw type (maximum permissible torque < 60 N/mm² as specified by the installation table).

3. Remove protective cap – Immediately before installation, remove the protective cover from the sensor probe. Do not allow any dirt to contaminate the lubricated threads. Do not wipe anti-wear agent from the thread surface.

4. Install the probe – Insert the sensor probe into the exhaust bung. Hand-tighten the hexagon nut while holding the sensor tip bottom section, contacting the metal retaining clip, to prevent cable twisting and bending.

5. Torque properly – Use a standard torque wrench to tighten the hexagon nut. Recommended torque for M20 x 1.5 threads: 50 Nm ± 10 Nm (40–60 Nm). After tightening, the maximum allowable cable rotation angle is 180°.

6. Connect the harness – Connect the mating 4-pin connector to the sensor. Ensure the connector interior is clean and dry. To prevent reverse connection, both plug and socket feature connection indexing marks.

7. Reconnect battery – Restore power after installation is complete.

A new NOx sensor must be properly reset and programmed to function correctly. The sensor must be replaced and reprogrammed in accordance with the vehicle manufacturer‘s specifications. Various error messages may occur if the sensor is not programmed accordingly.

Why adaptation is necessary: The stored NOx values from the old sensor must be deleted before the new sensor can function properly. Engine Control Units continuously learn and adapt to sensor degradation over time; installing a fresh component without resetting these learned values leaves your ECU operating on outdated data.

Recommended procedure:

1. Install the sensor following the sequence above

2. Connect a professional diagnostic scan tool capable of commercial vehicle diagnostics (SAE J1939 compatible)

3. Clear all existing DTCs – Use the diagnostic tool to clear all existing fault codes

4. Reset adaptation values – Navigate to the SCR/Emissions service menu and execute the command to reset learned values for the replaced component

5. If required, perform sensor programming – Some vehicle platforms require specific NOx sensor programming. The sensor must be replaced and reprogrammed in accordance with the vehicle manufacturer’s specifications

6. Perform drive cycle – Complete a 15–20 minute mixed driving cycle at operating temperature with varying engine loads

7. Verify readiness – After the drive cycle, check for any returning DTCs. Monitor live NOx data; it should fluctuate logically

Note: In most cases for this specific application, after ensuring the replacement sensor matches the original part numbers, you may only need to clear fault codes using a diagnostic tool after replacement to reset the system. However, adaptation may still be required depending on the specific vehicle platform. Always verify with your vehicle manufacturer‘s service documentation.

• 12V system confirmation: Unlike many other 5WK96xxx series NOx sensors that operate on 24V, the 5WK96674 / 5WK96674A is a 12V sensor. Verify your vehicle‘s electrical system voltage before purchase

• Wiring harness condition: Commercial vehicles operate in harsh environments (vibration, heat, moisture, road salt). Inspect the full harness length for chafing, corrosion at connectors, and damaged insulation before condemning the sensor

• SCR system health: A recurring NOx sensor code may indicate a failed SCR catalyst, DEF quality issues, or a clogged DEF injector. These should be diagnosed before replacing the sensor a second time

• Multiple sensor positions: This vehicle platform may use two NOx sensors (upstream and downstream of the SCR catalyst). The 5WK96674 / 5WK96674A is typically designated as the outlet (downstream) sensor. Verify which position requires replacement

• Replacing part numbers: When purchasing, the replacing part number may be listed as 5WK9 6674A, 2871978, or 2894939RX. Always confirm against your original sensor

• Emergency service: For breakdown or urgent fleet maintenance, some suppliers offer emergency-service channels for critical breakdown orders. Highlight “URGENT” in your inquiry to prioritize production and arrange express shipping (DHL, FedEx, UPS)

• In regions with mandatory emissions testing (EU, California, China, Australia, Brazil), a non-functioning NOx sensor will cause the MIL to illuminate, resulting in automatic inspection failure

• It is illegal to defeat, delete, or simulate the NOx sensor signal in any on-road vehicle. Always replace with a fully functional sensor

• The sensor is designed to detect NOx levels in diesel-fueled vehicles that must comply with state and federal emissions regulations. It is intended to restore drivability and proper engine function.

• The sensor is designed to optimize emissions and fuel economy to meet national and regional emission standards.

• Before purchasing, confirm the supplier offers a return or exchange for compatibility errors, preferably within 30 days of receipt

• Keep your original sensor until the new one is confirmed working – it serves as the ultimate reference for part number and fitment

• Request a data sheet or installation guide that includes pinout and programming steps if available

• Most reputable suppliers offer a 6–12 month warranty against manufacturing defects. Some offer one-year, unlimited mileage coverage

• Some suppliers offer a complete technical package (STEP/IGES/CAD files, manuals, test reports) for engineering, procurement, and maintenance workflows with bulk orders.

• For bulk orders, white-label and custom packaging services (including barcoding, fleet labeling) may be available.

The NOx Sensor 5WK96674 / 5WK96674A is a critical emissions aftertreatment component for 12V medium-duty and heavy-duty diesel commercial vehicles. Operating at 12V DC, this sensor is specifically designed for use as an Outlet / Downstream NOx sensor, installed after the SCR catalyst to verify emissions compliance.

Primary applications: Cummins diesel engines, particularly the ISB 6.7L (2010–2012) and ISX 15L (2010–2012) platforms, in commercial vehicles including Freightliner, Blue Bird, Kenworth, Peterbilt, International, Spartan, Western Star, and others.

Key cross-references: 2894939, 2894939RX, 2871978, 4984053, 4984576, 904-6004, A034X846, 5WK96674, 5WK96674A, 5WK9 6674A

Key technical specifications:

• Operating voltage: 12V DC (critical distinction – many other 5WK96xxx series sensors are 24V)

• Communication: Digital CAN bus (SAE J1939)

• NOx measuring range: 0–3000 ppm

• O₂ measuring range: 0%–21%

• Connector: Black flat 4-pin sealed

• Thread: M20 x 1.5

• Cable length: Approximately 590–795 mm

• Weight: Approximately 0.5 kg

• Torque specification: 50 Nm ± 10 Nm (40–60 Nm)

• Compliance: EPA10, RoHS, REACH, TS16949, CE

Installation requirements:

• Do NOT apply anti-seize to threads

• Do NOT wipe anti-wear agent from threads

• Do NOT touch ceramic sensing element

• Confirm 12V system voltage – DO NOT install on 24V vehicles

• Professional installation and ECU reset/adaptation required after replacement

• Perform torque to 50 Nm ± 10 Nm (40–60 Nm)

CRITICAL NOTE – VOLTAGE COMPATIBILITY: The 5WK96674 / 5WK96674A operates on 12V DC. This distinguishes it from many other NOx sensors in the 5WK96xxx series that are designed for 24V commercial vehicle applications. Always verify your vehicle‘s electrical system voltage (12V or 24V) before purchase. Installing this 12V sensor on a 24V system will cause immediate heater or electronics damage.

CRITICAL NOTE – ECU RESET IS RECOMMENDED: The sensor should be replaced and cleared of fault codes using an appropriate diagnostic tool. In most cases, after replacement, you should clear fault codes to reset the system. The sensor must be replaced and reprogrammed in accordance with the vehicle manufacturer‘s specifications; various error messages may occur if the sensor is not programmed accordingly.

Self-diagnostic technology: The sensor integrates advanced self-diagnostic function that automatically compensates for minor signal drifts and environmental variations, maintaining high-precision NOx concentration detection and consistent output over time.

Proper selection (matching the part number 5WK96674 or 5WK96674A), confirmation of 12V system voltage, careful installation using correct torque (50 Nm ± 10 Nm), and proper ECU reset/adaptation ensure full emissions compliance, optimal fuel economy, and reliable SCR system performance. Use this guide to confidently purchase and replace a failed 5WK96674 / 5WK96674A NOx sensor without compatibility issues or repeat failures.

For further technical support, refer to your engine or vehicle manufacturer‘s service documentation or consult a qualified diesel emissions specialist.