A Guide on Cummins NOx Sensor Problems
Nitrous oxide (NOx) is a prominent pollutant in diesel engines' exhaust. It is a significant contributor to air pollution and has been linked to health problems, so it's essential to control NOx emissions. As a result, it's mandatory in most countries that diesel engines like Cummins must be fitted with a specific type of after-treatment system called Selective Catalytic Reduction (SCR).
This is where Cummins NOx sensors come in, as they are an essential part of the SCR. The NOx sensor measures the amount of NOx present in the exhaust gas, and the after-treatment system then uses this information to control it accordingly. However, specific problems may arise with your Cummins NOx sensor, leading to poor detection of NOx levels.
This guide will discuss what causes NOx emissions from Cummins engines and how your machine can control them. So, let's dive right in.
What are NOx Sensors?
Nitrogen oxide (NOx) sensors measure the amount of NOx present in the exhaust gasses emitted from an internal combustion engine. This information is used to control the NOx levels in the exhaust gas using a selective catalytic reduction (SCR) system. This system uses urea (an ammonia-based substance) as an additive that reacts with NOx to produce harmless nitrogen and water as byproducts.
The NOx sensors come in two types: heated or unheated. Heated NOx sensors are usually used on diesel engines, as they require more energy than unheated sensors.
Working of NOx Sensor
A NOx sensor helps the SCR determine the correct amount of uric acid or ammonia for better fuel efficiency and lower emission levels.
This sensor works by measuring the amount of NOx in the exhaust. This is done by exposing a catalyst bed to an electric current that causes it to produce electrons.
The electrons then react with NOx to produce harmless nitrogen and water as byproducts. In addition, these sensors help determine if there is enough oxygen available for proper combustion. Otherwise, the engine will run lean, which can cause the engine to stall.
NOx Sensor Failure Symptoms
As with any vehicle sensor, NOx sensor failures can occur. Here are some of the most common NOx sensor failures and their associated warning signs.
High Fuel Consumption
One of the most common NOx sensor failures is high fuel consumption. This can be caused by an oxygen sensor not reading correctly, which causes your Cummins engine to run lean. A lean mixture will burn more fuel, leading to increased emissions.
Suppose the O2 sensors fail and cannot accurately measure the oxygen content in the exhaust gas. The ECU may be unable to determine the correct air/gasoline ratio for optimal performance. If your engine is running rough or hesitating, it may indicate that the NOx sensors in your exhaust system are not working correctly . If you have poor gas mileage on your Cummins, these may be issues you must address.
You can have these checked out by a mechanic or replace them if faulty. If you notice a dramatic increase in your vehicle’s fuel consumption, have it checked by a qualified professional.
Rough Idling
Rough idle may be caused by one or more of several different issues. Among them are faulty sensors, clogged air filters, bad ignition coils, dirty spark plugs, worn-out distributor caps, etc.
Typically, these issues are addressed by the DME (digital motor electronics), a digital systems and diagnostics monitoring device of your engine to compensate for specific issues. However, if the DME cannot access information on these issues, a rough idle will result. For example, this is often seen when there are problems with one or more oxygen sensors in your exhaust system.
Erratic Acceleration
If the engine controls don't compensate for an inaccurate reading from the NOx sensors, the machine may jerk when you press down on the accelerator. There are several reasons why an engine could misfire, including a bad fuel mixture, dirty or clogged air filters, and worn-out spark plugs. This can signify a bad fuel pump, injectors, or even a problem with the ignition coils.
However, if there is a sudden loss of power, then the NOx sensor could malfunction. This occurs when the DME needs more information about the engine's current state. This can happen if the oxygen sensor is dirty, clogged, or has fallen out of place. It could also occur if there is a problem with the wiring harness to your NOx sensor.
Frequently Asked Questions:
What is the difference between a NOx sensor and an O2 sensor?
An O2 sensor measures the amount of oxygen in the exhaust stream, while a NOx sensor measures the amount of Nitrogen Oxide (NOx). Both types of sensors work together to ensure that the emissions produced by your engine meet federal standards.
Why does my car run so much worse after installing new NOx sensors?
This is because you must calibrate the NOx sensors before they function correctly. Your mechanic will need to recalibrate the sensors using special software.
What is the SCR?
SCR stands for selective catalytic reduction, which converts NOx into N2 and H2O, thus reducing the level of harmful gasses emitted by the car.
What if my truck's NOx sensor is faulty?
If you drive your vehicle with an incorrect mixture setting, the engine may run rich and use too much DEF, but the ECM will eventually cause the engine to enter limp modes and decelerate.
What is the most common fault code associated with a bad NOx sensor?
The most common faults related to bad SCR inlet NOx sensors are SPN 3217FMI3 (SCR inlet NOx sensing circuit, failure closed), SPN 3217F MI5 (SCR inlet Nox sensing circuit, failure open), SPN 3 227 FMI 3 (SCO outlet NOx sensing circuit, failure re-closed) and SPN 3 227 F MI 5 (SCO outlet NOX sensing circuit, failure open).
Discover Cummins NOx Sensor Tips at Heavy Duty Pros
Overall, Cummins NOx sensors are critical to your engine's emissions system. If you're having trouble with your NOx sensor, it's essential to have it checked out by a professional. At Heavy Duty Pros , we offer every product for your sensor needs. Visit our website for more information.