Scr outlet nox sensor ppm

Log in. Forgot your password? Forgot your username? Create an account. Please Log in or Create an account to join the conversation. Buy The Book! Index Recent Topics Search. Log in Username. Remember me. Log in Forgot your password? Start Prev 1 Next End. Im curious about NOx sensor testing and values to look for. From what i know, NOx sensors are basically oxygen sensors that are designed to break down the NOx and measure the O2 in the gas.

Back probing the sensor for voltages is out unless you pierce the wiring between the module and sensor and all voltages you see in the scan tool is all processed data which may or may not output raw voltages during a fault or even output quick enough. I assume they also have a heater element? Anyone know more about these sensors and how they can be used to diagnose running conditions?

Confirm what it's not, and fix what it is! Last edit: 12 Oct by graywave. You've got about as much info as I do. I can go over my class manuals when I get home in case I missed anything. GM is the same way, not sure about Ford. I've used rationality testing several times while catching lying NOx sensors. There's no rational way that NOx readings should be higher after the SCR, which means one sensor or the other is skewed.

MacFadyen Replied by Andy.Welcome to world's most trustworthy automotive forum. Thread Rating: 72 Vote s - 2. Reputation: 4. We had a customer bring in a Freightliner with a DD13 in today with a check engine light on. I have checked the quality of the DEF fluid and it is good. I also performed the DEF quantity test and it worked perfect. I then performed a parked regen and kept an eye on the inlet and outlet NOx sensors. During the regen the outlet NOx was higher than the inlet NOx nearly the entire time.

After that I pulled the one box off the truck and pulled out the DPF filters. We are probably going to go ahead and have the DPF filters cleaned while they are out. I've heard a little bit about the other catalysts inside the one box failing. I was able to look at the DOCs with a borescope and didn't see any signs of damage but there is absolutely no way to see the inlet of the SCR this is an awful design.

Any idea what I need to check next? Reputation: Visually they look ok. While running the regen the inlet was showing about ppm and the outlet was showing about ppm. As soon as the engine idled back down the inlet was showing about ppm and the outlet was showing about ppm. I'm currently downloading dddl8. We are sending the DPF filters off to get cleaned and when they get back I will hook back up to the truck and run the test. I was able to look at the DOC face with a borescope and they looked to be plugged.

The one box got sent out to be cleaned today. When I get it back I will post the results. Reputation: 2. I would check Nox Sensor. They can be bad and giving active faults. Once you replace them delete fault codes and run parked regen and wait until it finishes.

If there is no change and have new or same codes active continue searching for the reason. Also SCR doser can be plugged it's easy to check.

Reputation: 8. I am unsure if I should be posting at the moment seeing how I have just joined this group however I work on a lot of different Regen systems and Nox sensors would be a great place to start but more curious to me is what temps was the system seeing during the regen process? Reputation: 4, Here's the "normal" values for all of the Aftertreatment Parameters during a Parked Regen.

I didn't save the log file when I ran the regeneration but I believe the temps were around F. I have already checked the DEF system and it is good. I'm hoping to get the one box back tomorrow.Discussion in ' Freightliner Forum ' started by janboskitJun 28, Each company we work with has specific experience requirements for their drivers.

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Jun 28, Same issue on my Cascadia DD15 engine. In short, eventually needed a new onebox. Got it while it was still in warrantee. SinghJun 28, Name Email Phone Yes, let employers and TruckersReport text me with new opportunities, job alerts and other career information to the number I provided.

There is no charge for this service, but standard message and data rates may apply. Now that these have been out a few years we may see this issue more often. Jun 29, They are built into the Onebox system and can't be changed like the DPF filter. They did try a special cleaning mode that Freightliner can run. Its basically last chance try.

It cracked my DOC filters or something was rattling after they did the cleaning. The emissions box was no good. I got out of owning my own truck at that point. BrandtJun 29, Intothesunset and uncleal13 Thank this. SLCTruckerJun 29, There's a member on here named mhyn that's technically knowledgeable with his freightliners. He's got the diagnostic software I believe.

Intothesunset and mhyn Thank this. Yup my total cost would've been near the same had it been out of warranty.

scr outlet nox sensor ppm

I opted for new filters too at the time. SinghJun 29, Jul 21, They shouldn't be more then 50PPM apart and that will verify your inlet and outlet NOx sensors are not drifting. Last edited: Jul 21, Jul 25, Intothesunset Thanks this.

Show Ignored Content. Draft saved Draft deleted. Your username or email address: Do you already have an account? No, create an account now. Yes, my password is: Forgot your password?Revision This is a preview of the paper, limited to some initial content. Full access requires DieselNet subscription.

scr outlet nox sensor ppm

Please log in to view the complete version of this paper. The development of exhaust gas NOx sensors started in the s. Commercial sensors were first introduced in the early s on lean-burn, stratified charge gasoline passenger cars with NOx adsorbersfollowed by diesel cars with NOx adsorbers and light- and heavy-duty diesel engines with urea-SCR aftertreatment.

Eventually, all stratified charge gasoline engines in the Volkswagen Group 1. After a few years, however, the use of stratified charge engines and the associated market for NOx sensors started to decline, due to the lower than expected CO 2 emission benefits and the high cost of NOx adsorber aftertreatment. Volkswagen bid farewell to stratified charge engines inand BMW followed suit five years later. Another area of NOx sensor application has opened with the introduction of NOx adsorber catalysts on light-duty diesel engines.

The technology was widely adopted on diesel cars—primarily in Europe, but also in the US and other markets—including models from Volkswagen, BMW, and Daimler.

scr outlet nox sensor ppm

These vehicles were typically equipped with a NOx sensor after the NOx storage catalytic converter. The most recent area of NOx sensor application are urea-SCR systems for light- and heavy-duty diesel engines. If two sensors are installed, the conversion rate of the SCR catalytic converter can be easily determined.

The NOx limits may be lowered to values as low as 0. Improved sensor performance would not only be required for potential changes to OBD thresholds but also for in-use emissions monitoring that is being proposed as an alternative to the more conventional durability demonstrations.

NOx sensor technology would need to develop further to be able to monitor emissions at low NOx levels, over the whole duty cycle of heavy-duty vehicle operations, and over their entire useful life. The most common in-situ NOx measurement technology relies on yttrium-stabilized ZrO 2 YSZ electrochemical sensors []similar in construction and operating principle to broadband oxygen sensors.

The YSZ sensors are discussed in detail in the following sections. The two final sections of this article cover, respectively, new NOx sensor developments and ammonia sensors. The latter technology, based on the same YSZ electrochemical system, has been commercialized in some SCR applications, but its use remains limited.

Commercial NOx sensors for automotive applications are primarily YSZ electrochemical sensors of the amperometric type. Figure 1 illustrates the basic operating principle. The sensor uses two or three electrochemical cells in adjacent chambers. The first cell electrochemically pumps O 2 out of the sample so it does not interfere with the NOx measurement in the second cell.

The need to remove O 2 allows this type of NOx sensor to serve a dual purpose; it can also detect exhaust O 2 level. The O 2 in the first cell is reduced and the resulting O ions are pumped through the zirconia electrolyte by applying a bias of approximately mV to mV. The pumping current is proportional to the O 2 concentration.

The remaining gases diffuse into the second cell where a reducing catalyst causes NOx to decompose into N 2 and O 2. As with the first cell, a bias of mV applied to the electrode dissociates the resulting O 2 which is then pumped out of the cell; the pumping current of the second cell is proportional to the amount of oxygen from the NOx decomposition.

EPA 10 DDE 15 Regen Log File Normal Values

An additional electrochemical cell can be used as a Nernstian lambda sensor to help control the NOx sensing cell []. Several chemical elements were also selected as potential electrode materials, including platinum, rhodium and palladium.

The system that has been most widely adopted and used in almost all commercial NOx and lambda sensors is based on solid state yttrium-stabilized zirconia electrolyte the same material that was used in the Nernst lamp.Revision This is a preview of the paper, limited to some initial content.

Full access requires DieselNet subscription. Please log in to view the complete version of this paper. While very high conversion efficiencies with urea-SCR NOx aftertreatment systems are possible using simple dosing approaches, the combination of high conversion efficiency, minimum urea consumption and minimum ammonia slip is much more difficult to achieve. The ultimate objective of urea dosing control then is to lower tailpipe NOx emissions sufficiently to meet regulatory limits over the required test cycles and to meet the additional requirements of low ammonia slip and urea consumption.

To be available for the conversion of NOx to N 2ammonia must adsorb onto the SCR catalyst where it can then participate in the in the NOx reduction chemistry. While there are numerous factors that impact SCR conversion efficiency, ammonia storage on the SCR catalyst is one important one that can influenced by the urea dosing control system; the more ammonia that is stored on the catalyst, the higher the NOx conversion, Figure 1 [].

However, under conditions such as increasing catalyst temperature Figure 2ammonia can be desorbed from the catalyst and result in the release of unreacted ammonia—ammonia slip []. The more ammonia that is stored on the catalyst at low catalyst temperatures, the more that would be released when ammonia slip conditions are encountered. Typical limits for ammonia slip are 10 ppm average and 30 ppm maximum. In practical terms then, the urea dosing control problem then becomes one of storing sufficient ammonia on the SCR catalyst to achieve the required emission targets while limiting ammonia slip to the required limits.

A number of urea dosing strategies are available. The choice of strategy depends on a number of factors including: the SCR catalyst NOx conversion required, the allowable ammonia slip limits, drive cycle effects and the requirements for long term system robustness.

Open loop strategies primarily control the rate of urea dosing based on values contained in look-up tables or maps. The look-up table may contain multiple variables including exhaust temperature, engine speed and engine load. Closed loop control strategies use a sensor to provide feedback and are thus able to adjust urea dosing to more accurately reflect operating conditions and to account for long term drift.

Aftertreatment Outlet NOx (ppm)

Newer approaches are available that use an ammonia sensor located somewhere after the front section of the SCR catalyst. Virtual sensors, where a particular parameter such as catalyst outlet NOx is modeled based on the input from other sensors, are also used.

For urea dosing, system dynamics make pure closed loop control very difficult and most closed loop strategies rely heavily on an open loop strategy to provide feedforward control.

SCR inlet NOx can be assumed to be held constant. As urea dosing rate increases, more ammonia is available to convert NOx to N 2. This yields the increase in SCR efficiency.

This leads to the increase in NH 3 emissions as urea dosing rate increases. However, commonly used NOx sensors are cross-sensitive to NH 3 emissions so the NOx sensor signal starts to increase again as NH 3 slip increases [].

Urea Dosing Control

Superimposed on Figure 3 are some potential SCR efficiencies using open loop control and closed loop control. It should be noted that these potential conversion efficiencies represent only one view of this matter from the mids and the chart should be interpreted qualitatively rather than quantitatively.

The SCR control approaches shown in the chart can be summarized as follows:. However, as demonstrated by commercial applications of high efficiency SCR systems using an NH 3 sensor, an NH 3 slip catalyst may still be required Figure On the other hand, signal processing techniques have been developed to account for the NH 3 cross sensitivity of NOx sensors.

Abstract : Early applications of urea-SCR technology on mobile diesel engines utilized open loop, or feedforward, control of urea dosing. In a common approach, a number of control strategies have been using two NOx sensors—one positioned upstream, the other downstream of the SCR catalyst.

Model-based, adaptive SCR control strategies using an ammonia sensor have also been developed.Emissions regulations for internal combustion engines have become more stringent over recent years. Environmental concerns have motivated the implementation of stricter emission requirements for internal combustion engines throughout much of the world.

Governmental agencies, such as the Environmental Protection Agency EPA in the United States, carefully monitor the emission quality of engines and set emission standards to which engines must comply. Consequently, the use of exhaust aftertreatment systems on engines to reduce emissions is increasing.

Exhaust aftertreatment systems are generally designed to reduce emission of particulate matter, nitrogen oxides NOxhydrocarbons, and other environmentally harmful pollutants. However, the components that make up the exhaust aftertreatment system can be susceptible to failure and degradation. Because the failure or degradation of components may have adverse consequences on performance and the emission-reduction capability of the exhaust aftertreatment system, the detection and, if possible, correction of failed or degraded components is desirable.

In fact, some regulations require on-board diagnostic OBD monitoring or testing of many of the components of the exhaust aftertreatment system.

When equipped on vehicles, most monitoring and testing of aftertreatment system components are performed during on-road operation of the vehicle e. Although such monitoring and testing may be convenient, the efficacy of the monitoring and testing may be limited because the engine cannot be operated outside of a given on-road calibrated operating range.

Additionally, because on-road operating demands typically have priority over diagnostic and performance recovery procedures, the order, timing, and control of such procedures may be less than ideal.

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As a result, the detection and correction of various failure modes in the exhaust aftertreatment system may be limited. One embodiment relates to an apparatus including a dosing module, an engine module, a selective catalytic reduction SCR inlet NOx module, a SCR outlet NOx module, a phase correction module, and a system diagnostic module. The dosing module is structured to suspend dosing in an exhaust aftertreatment system.

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The engine module is structured to provide a command to an engine to affect an engine out nitrogen oxide NOx amount. The system diagnostic module is structured to determine a diagnostic feature based on the SCR inlet NOx data and the phase shifted SCR outlet NOx data, wherein the system diagnostic module is structured to determine a state of the SCR inlet and outlet NOx sensors based on the diagnostic feature, the state including at least one of an operational state and at least one of the SCR inlet and outlet NOx sensor are faulty.

The apparatus provides a service technician the ability to diagnose exhaust aftertreatment problems to the SCR inlet and outlet NOx sensors, which thereby alleviates the need for costly and timely service diagnostics regarding the whole exhaust aftertreatment system.

Another embodiment relates to a method for diagnosing NOx sensors in an exhaust aftertreatment system. According to one embodiment, the method is performed as an intrusive diagnostic tool for an engine and exhaust aftertreatment system, wherein the method controls operation of the engine and exhaust aftertreatment system.

Another embodiment relates to a system including an engine; an exhaust aftertreatment system in exhaust gas receiving communication with the engine, wherein the exhaust aftertreatment system includes a selective catalytic reduction SCR system; and a controller communicably coupled to the engine and the exhaust aftertreatment system. These and other features, together with the organization and manner of operation thereof, will become apparent from the following detailed description when taken in conjunction with the accompanying drawings.

Referring to the Figures generally, the various embodiments disclosed herein relate to a system and method of diagnosing NOx sensors in an exhaust aftertreatment system. According to the present disclosure, a controller performs an intrusive diagnostic procedure that manipulates a NOx amount out of an engine, measures the resulting NOx amount across a selective catalytic reduction SCR system, and determines whether among other failure modes the NOx inlet and NOx outlet sensor are faulty by utilizing one or more diagnostic features, which are described more fully herein.

As a brief overview, some engine systems include exhaust aftertreatment systems for decreasing the pollutants emitted from the engine systems. Among other components, these exhaust aftertreatment systems may include a SCR system.

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The SCR includes a SCR catalyst that is designed to reduce the nitrous oxides NOx in engine exhaust gas to nitrogen and other less pollutant compounds. To accomplish this reduction, a reductant is sprayed into the exhaust gas stream prior to the exhaust gas reaching the SCR system. Over the SCR catalyst, the NOx reacts with ammonia that formed from the decomposition of the reductant, to form nitrogen and other less harmful compounds.

In turn, a decrease in NOx emissions from the exhaust gas is accomplished. The efficiency of the SCR catalyst may be determined by measuring the reduction of NOx emissions from the exhaust gas between the inlet to the outlet of the SCR catalyst, which is described more fully below. In certain embodiments, SCR efficiency may be determined by a NOx conversion fraction for the exhaust gas.This code will put the unit in a derate for at least one drive cycle but will not shut down the unit.

I have a dd When the engine is put under stress 25,lbs or more in hilly terrain I get fault code nox conv eff.

When these 2 faults come at same time I will have the yellow light in fuel gauge flash. If I am able to park sometimes it will let me manually regen.

My question is this a pressure problem emission control valve.

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I have the one box system I have the following faults and when engine is under stress 15, lbs it blows out white smelly smoke from the tailpipe and it even goes into the cab!

Scr Inlet snsrnox efficiency low,low temp regen. Perform a regen to verify code. Verify for any air system related fault codes, if any repair those first. Verify for any EGR related faults, if any repair those first. Verify for any DEF related faults, if any repair those first.

Selective Catalyst Reduction NOx Conversion Very low 4361/1 & 4364/18

If any repair those first. Check DEF quality, verify there is no contamination. Make sure they are within 4. Spec is between ml. If not replace and regen to verify repair.

After all basic checks have been performed. Leave a Reply Cancel reply Your email address will not be published.

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