5W Electrochemical Auto NOx Sensor 4326863 5WK96765A 5WK96765B 5WK96765C

5WK96765A/5WK96765B/5WK96765C Car NOx Sensor Nitrogen Oxide Sensor 4326863/5334965

The 5WK96765A is a planar dual-cell limiting current type nitrogen oxide (NOx) sensor designed for 24V medium-duty and heavy-duty diesel engine exhaust aftertreatment systems. It is an electrochemical sensor that continuously measures the concentration of nitrogen oxides (NOx) and oxygen (O₂) in the exhaust stream and communicates with the engine control unit via digital CAN bus protocol. This real-time feedback enables precise control of the Selective Catalytic Reduction (SCR) system, ensuring compliance with Euro V, Euro VI, EPA, and equivalent emission standards.

The sensor consists of a ceramic sensor element and an electronic control unit (ECU), which measures the NOx concentration, air/fuel ratio (A/F ratio), and equilibrium oxygen partial pressure in the exhaust gas of combustion engines, suitable for both gasoline and diesel applications.

The sensor is made up of a Nernst cell with a current flowing through it, which corrects the air/fuel ratio to λ=1. A second cell, typically made of ceramic with a layer of rhodium, breaks down the oxides of nitrogen into nitrogen and oxygen. The NOx controller—usually positioned close to the NOx sensor—calculates the level of oxides of nitrogen present in the exhaust gas and sends that data to the SCR controller. The SCR controller then adjusts the amount of Diesel Exhaust Fluid injected into the SCR catalyst, which in turn transforms excess oxides of nitrogen into water and nitrogen.

The NOx sensor transmits the NOx value in the exhaust gas to the ECU in real time after normal operation. The ECU monitors whether the NOx value in the exhaust gas exceeds the standard through a set of nitrogen oxide monitoring programs.

Important: The 5WK96765A operates on a 24V system voltage. It is specifically designed for commercial vehicle applications, including trucks and buses equipped with SCR aftertreatment systems. Do not install on 12V passenger car systems as the electronics and heater are calibrated for 24V operation.

The following part numbers are directly interchangeable with 5WK96765A. 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, and voltage rating before purchasing.

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

• 4326863, A045S157 – documented as OEM cross numbers for 5WK96765A

• 4326863, 4326471, 4307260 – listed as equivalents

• 4326863, 5WK9 6765A, 5WK96765A, 5WK9 6765B, 5WK96765B – direct replacements

⚠️ Suffix and supersession caution: Different suffixes (A vs. B) may indicate minor production revisions or calibration differences. While these variants are generally interchangeable, different suffixes may have distinct CAN message IDs or heater calibration parameters. Match the full alphanumeric string on your original sensor whenever possible. Do not rely solely on partial number matches. The suffix B variant is typically considered a later production revision that supersedes suffix A in many applications.

The 5WK96765A NOx sensor is designed for 24V commercial vehicle electrical systems and is widely used across medium-duty and heavy-duty diesel engine platforms. Application coverage spans Euro V / Euro VI compliant commercial vehicles, including trucks, buses, and industrial machinery.

This sensor is most commonly associated with Cummins diesel engines in commercial vehicle applications. It is identified as a critical component for Cummins engine emission control systems, particularly for medium and heavy-duty applications. The sensor is specifically compatible with:

• Cummins engine – Medium and heavy-duty diesel platforms (primary application)

• Cummins ISF series – Light-duty and medium-duty diesel engines

• Cummins ISB/ISBe series – Medium-duty truck engines

• Cummins ISC/ISL series – Heavy-duty truck engines

• Cummins QSB/QSL series – Industrial and off-highway applications

Based on compatibility listings, the 5WK96765A has been verified for the following applications:

This sensor is also cross-referenced for use with Mack and Renault diesel applications, indicating broader compatibility across European commercial vehicle platforms.

The 5WK96765A is found in a wide range of 24V commercial vehicle applications:

• Heavy-duty trucks – long-haul and regional transport

• Medium-duty trucks – delivery and utility vehicles

• Buses and coaches – public transportation and commercial coach applications

• Construction equipment – diesel-powered machinery with SCR aftertreatment systems

• Agricultural equipment – SCR-equipped diesel farm machinery

The sensor operates on a 24V power supply and includes ECU programming compatibility. This makes it suitable for most European, North American, and Asian heavy-duty diesel platforms manufactured after the introduction of SCR-based emissions compliance systems. The sensor is widely used in the SCR aftertreatment systems of diesel trucks and buses requiring Euro V and Euro VI emissions compliance.

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 including suffix (A, B, etc.)

2. Verify voltage – The 5WK96765A is a 24V sensor; confirm your vehicle electrical system is 24V

3. Count connector pins – Black square 4-pin plug type

4. Measure cable length – Approximately 590 – 600 mm

5. Check ECU compatibility – Some platforms require software adaptation after sensor replacement

6. Confirm thread size – M20 x 1.5 external thread (verify against original)

⚠️ Important note: Compatibility extends beyond physical fitment. The sensor must match the ECU‘s CAN communication protocol. Different vehicle manufacturers may use different calibration parameters even when the physical sensor appears identical. Always reference your original sensor part number or consult vehicle-specific documentation before purchasing.

The specified mounting position of the NOx sensor is typically downstream of the NOx trap or upstream/downstream of the SCR catalyst, depending on the specific vehicle platform configuration. Verify the correct mounting position on your vehicle before installation, as some platforms utilize two NOx sensors (upstream and downstream) while others use only one.

A degraded or failed 5WK96765A 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 of a failing NOx sensor is the illumination of the check engine light on the dashboard, indicating a potential issue with the emission control system. The ECU detects an out-of-range voltage, missing CAN message, or implausible NOx reading. On commercial vehicles, this appears as a CEL (Check Engine Light) or MIL on the dashboard.

When NOx readings become inconsistent or implausible, the ECU reacts to protect emissions systems by limiting torque and engine speed. Commercial vehicles may experience speed limitation (typically 5-20 mph or restricted RPM) until the issue is resolved. This is commonly referred to as “limp mode” and is designed to prevent further damage to the aftertreatment system.

False high NOx readings cause the SCR system to over-dose DEF, resulting in rapid AdBlue depletion and potential crystallized injector. This is one of the most costly indirect symptoms of a failing NOx sensor, as excessive DEF consumption not only increases operating costs but can also lead to injector clogging and further system damage.

Without accurate NOx feedback, the ECU reverts to conservative fuel maps or adjusts EGR rates. Fuel consumption can increase by 15-25% as the engine operates in a suboptimal state. This symptom may be gradual and often goes unnoticed until other symptoms appear.

Overdosing of DEF leads to ammonia slip (NH₃), which may be visible as white vapor with a sharp, pungent odor exiting the tailpipe. This indicates that excess DEF is being injected into the SCR catalyst and not being fully consumed in the reduction reaction.

The SCR system cannot effectively reduce NOx without accurate sensor feedback, causing tailpipe NOx to exceed legal limits. This results in automatic failure during emissions testing, which can ground commercial vehicles and result in compliance violations.

A failing NOx sensor can result in engine misfires, hesitation during acceleration, and unstable idling, affecting the vehicle’s overall performance and driveability.

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 sensor to operational temperature quickly after engine startup, especially in cold ambient conditions.

Common codes associated with NOx sensor failure include:

The P207F code is specifically associated with failure of NOx sensors or modules, particularly faulty upstream (before SCR) or downstream (after SCR) sensors, or J1939 communication network failure linking NOx modules to the engine control unit.

One characteristic symptom of a failing NOx sensor is repeated warnings that return after being cleared with a diagnostic tool. If a DTC related to the SCR or NOx sensor returns shortly after being cleared without any other work performed, it strongly indicates a persistent sensor or system fault.

Before replacing the 5WK96765A, perform these basic checks:

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

2. Heater resistance test – Measure between heater positive and heater ground pins using a multimeter. Typical resistance at 20°C is between 3-15 Ω. An open circuit or short indicates internal failure

3. Voltage supply – With key on and engine off, verify 24V power at the sensor connector

4. CAN bus integrity – Check CAN High and CAN Low lines for proper termination and absence of short circuits to ground or battery

5. Live data review – Using a diagnostic scan tool, observe NOx readings with key on, engine off. It should read ambient air values (0-30 ppm). 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, a contaminated SCR catalyst, or J1939 communication issues on the vehicle‘s CAN network. Perform a thorough system diagnosis before sensor replacement to avoid repeat failures.

Purchasing the correct 5WK96765A NOx sensor and installing it properly is essential for reliable SCR performance and avoiding costly mistakes. Commercial vehicle operators should pay special attention to electrical and communication compatibility.

• Match the full printed number on your original sensor, including the suffix (A, B, etc.). Different suffixes may have different CAN message IDs or heater calibration parameters

• Check supersession information – The suffix B variant is often a later production revision that may supersede suffix A. If your original part is 5WK96765B, verify compatibility before using 5WK96765A

• Avoid “universal fit” listings – The 5WK96765A is a specific digital device; generic sensors claiming to fit “all 24V diesels” are unlikely to communicate correctly with your ECU

• Reputable supplier – Choose a supplier with documented quality control (IATF 16949 or ISO 9001 certification) and a minimum 12-month warranty

• Avoid used or “remanufactured” – NOx sensors degrade internally from heat and contamination. Used sensors almost always fail prematurely

• Price guideline – Authentic quality replacements typically range from $65 to $120 for standard aftermarket options. Suspiciously low prices may indicate counterfeit or defective products

• Packaging – New sensors should be shipped in anti-static, moisture-proof packaging with a protective cap over the ceramic tip

• Certification – Look for suppliers with TS16949 and CE certification, indicating quality management system compliance

• 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

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

• Use appropriate tools – Use clean, dry tools. If mechanical damage is found on the sensor, do not install it

Follow this sequence for proper installation:

1. Prepare the mounting location – Ensure the exhaust bung threads are clean and free of debris

2. Remove protective cap – Remove the protective cover from the sensor probe only immediately before installation

3. Install the probe – Insert the sensor probe into the exhaust pipe bung. Hand-tighten the hexagon nut while holding the sensor body to prevent cable twisting

4. Torque properly – Recommended torque: 40–60 Nm (50 ± 10 Nm) for M20 x 1.5 threads

5. Connect the harness – Connect the mating 4-pin connector to the sensor. Ensure the connector interior is clean and dry. Lock the connector securely in place

6. Secure the cable – Use original routing clips and standoffs to secure the harness away from heat sources and moving parts

A new NOx sensor will not function correctly until the ECU learns its baseline values and performs a plausibility check. Many returns are caused by skipped adaptation, not a defective part. Follow these steps:

1. Install the sensor and securely connect the wiring harness

2. Clear all existing DTCs using a professional scan tool capable of commercial vehicle diagnostics (e.g., J1939 compatible tool)

3. Perform “NOx sensor replacement adaptation” – This function is typically found under “Special functions,” “SCR system,” or “Aftertreatment service” in diagnostic software. The ECU may command a specific warm-up sequence (often including holding the engine at elevated RPM for several minutes)

4. Reset SCR learned values (if available) – This clears previously stored efficiency values from the old, potentially faulty sensor

5. Perform a forced SCR system test – If your diagnostic tool supports it, run a forced SCR efficiency test to verify proper sensor operation

6. Drive cycle – Complete a 15-20 minute mixed driving cycle at operating temperature. For commercial vehicles, this should include both city and highway conditions with varying engine loads

7. Verify readiness – After the drive cycle, check for any returning DTCs. Monitor live NOx data: it should fluctuate logically (higher readings under heavy load, lower readings at idle)

Without proper adaptation, you may still see DTCs (e.g., P2200, P229E) even with a brand new sensor. Many returns are caused by skipped adaptation, not a defective part.

• 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: Some vehicle platforms use two NOx sensors (upstream and downstream of the SCR catalyst). Verify which position requires replacement. The 5WK96765A may be used in either position depending on the application

• ECU software updates: In some cases, a recurring NOx sensor issue may be addressed by an ECU software update rather than repeated sensor replacement

• J1939 network issues: NOx sensors communicate via the J1939 CAN network. If the vehicle has other communication-related faults, address those first as they may cause apparent NOx sensor faults

• 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

• Commercial fleets subject to emissions auditing must maintain properly functioning SCR systems, including accurate NOx sensing

• 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 adaptation steps for your specific application if available

• Most reputable suppliers offer a 12-month warranty against manufacturing defects

The NOx Sensor 5WK96765A is a critical emissions aftertreatment component for 24V heavy-duty and medium-duty diesel commercial vehicles. It provides real-time NOx and O₂ measurement to the ECU for precise SCR control, enabling compliance with Euro V and Euro VI emission standards.

Designed for Cummins diesel engine applications, this sensor is widely used in commercial vehicle platforms including Dongfeng, Fukuda, and Jianghuai trucks and buses. The sensor features a black square 4-pin connector, approximately 590-600mm cable length, and M20 x 1.5 external threads.

Proper selection (matching part number 5WK96765A or cross-references 4326863, A045S157, 4326471, 4307260), confirmation of 24V system voltage, careful installation using correct torque (40-60 Nm), and mandatory ECU adaptation ensure full emissions compliance, optimal fuel economy, and reliable SCR system performance. Use this guide to confidently purchase and replace a failed 5WK96765A 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.