Understanding Your EGR and DPF as a Truck Owner
02-21-2016, (Subject: Understanding Your EGR and DPF as a Truck Owner ) 
Post: #1
Understanding Your EGR and DPF as a Truck Owner
Understanding Your EGR and DPF as a Truck Owner...

If you have a truck that is newer than 2004, then the engine is most likely to be an EGR engine. Exhaust Gas Recirculation (EGR) is a fancy technical term used to describe the fact that some of the engine exhaust gas is returned back into the intake. To put this into perspective along with its effects, lets imagine for a moment that you are an athlete well trained in running marathons. One day, the California Air Resources Board (CARB) and the EPA decide they no longer like marathon runners because they breathe up too much oxygen and fart too much during races. To stop them from using up all the oxygen, they decide to make a law limiting the amount of fresh air all younger athletes are allowed to breathe. Now, for all new athletes, when they are in California, they must breathe through a paper bag with a small hole in the end of it at all times. Breathing through a paper bag with a tiny hole, definitely limits your oxygen intake, and trying to run a marathon like that will seriously slow you down, hopefully making you fart less as well. EGR to a diesel engine is what the 'Paper Bag' is to the athlete. It limits the amount of oxygen to the engine by starving it of clean air, making it re-breathe already used up air from the exhaust. The result is that the fuel cannot burn as hot, making it produce less harmful exhaust gases.

Now that you know what EGR actually does, why would it be so important for an owner-op to know about it, its parts, and its technical details?,... Isn't that what a mechanic is for?,... Theoretically yes, that is what a mechanic is for, and theoretically yes, they are supposed to fully understand these systems and their effects, but realistically, when your truck ends up in a repair shop over these kinds of problems, the mechanic is only there to solve the problem well enough to get your truck back onto the road, and out of their shop, rather than taking the time to go through your entire EGR system to ensure everything is clean and functioning properly. If you are very lucky, the mechanic will find the problem and correct it, but most of the time, what happens is that the truck ends up in the shop over and over, costing you thousands and thousands in repair bills and lost revenue. The only way to prevent this is to either get really lucky and not have any problems (possible but highly unlikely), or to take a proactive stand to prevent it. I, myself like to hang onto every last red cent and not give it to some repair shop, especially if it is something I can learn to do myself.

Most shops do actually care about getting your truck fixed right, but when it comes to EGR and DPF problems, most often, they are unwilling to go the extra steps to ensure your particular truck is at its peak performance. I have had more than one shop owner tell me that it is much more profitable for them to 'Patch You Up' and get you out of there, then onto the next truck, than it is to linger on one truck, trying to fix all its problems.

In any case, it is still far less costly to educate yourself toward these systems, than to rely solely on a repair shop, even if your not performing the work yourself. The ideal thing to do, is learn how to do the easier things yourself, saving you literally thousands, and only pay someone to do the things that you cannot do yourself when it comes to repairs, or component replacement. The key to all of this, especially if you will need a shop to perform any EGR or DPF related work for you, is to know enough to be able to direct them toward finding and solving the actual problem(s). You also need to know enough to direct them past the problem, performing relevant maintenance, so that repeat visits are prevented as well.

Everyone benefits from shared knowledge, so if you do find yourself in a shop, getting repairs or service work done, EGR or not, knowing enough to oversee and discuss what the shop has to do for you will always have a huge impact on how well things go. After all, YOU ARE PAYING THEM, not the other way around. Armed with the right information, you will also be able to quickly see if the repair shop you have chosen is going to be right for you as well.

What does EGR and the EGR Valve do?,...

The purpose of EGR itself, no matter what type or brand of diesel engine, is there to make the fuel burn at sort of a 'sweet spot' temperature to minimize harmful exhaust gases, while still providing as much energy as possible. The exhaust gas temperature (EGT) should be 570 degrees Fahrenheit give or take about 50 degrees when this is happening. The Engine's computer (ECM) monitors the exhaust, via a temp. sensor, making changes, opening or closing a valve that controls how much exhaust gas is sent back around to the intake. This valve is called the EGR valve. When the EGR valve is closed all the way, the engine will run on pure, clean air provided by the turbo, and when it is open all the way, the engine will be re-breathing, depending on your engine, up to about 40% of exhaust instead of nice clean air. This mixture of clean and dirty air needs to be pretty accurate for your truck to get good fuel economy, so if something isn't operating quite right, then your wallet is the first thing to suffer, long before any actual faults occur. To sum it up, your EGR valve controls the dirty air, and your turbo controls the clean air going into your engine. If either system is leaking, restricted, or otherwise not working properly, fuel economy goes down, and if it gets bad enough, it could shut you down with a fault.

The clean air side of your engine...

Starting with the clean air side of things, clean air is sucked in through the engine air filter, then gets pressurized by as much as 30+ PSI by the turbo. Compressed air gets hot, and wants to expand, so to prevent this, the pressurized, hot, expanded air is then sent through the air radiator (called a charge air cooler), cooling it off again. this makes that now pressurized air cooler, and more dense, making your fuel burn hotter, and providing that extra horse-power to climb hills with, but before it gets pushed into your engine, it gets mixed with Exhaust gases (dirty air), so that combustion temperatures can be lowered. The ECM precisely controls this clean air system by altering the speed of the turbo, changing the air pressure, as well as adjusting your EGR Valve. The air pressure itself is determined by several sensors that the ECM monitors. Some engines have more sensors than others, so I will just mention them them all. To pre-determine the oxygen content of the air, the ECM needs to know the current altitude, humidity, and temperature. This mini 3-sensor weather station can tell if you are on the beach, or if you are climbing Veil Pass. After all, the air is pretty thin at 12,000 feet. There is another temp sensor, just to verify that the 'weather station' is accurate mounted right at the turbo intake pipe as well. All those sensors are just to tell the ECM what the air quality is. From there, the ECM keeps an eye on the turbo itself through the use of a speed sensor (mounted on the turbo, usually having a slightly-thick green wire), just to make sure the turbo doesn't spin too fast. The ECM also uses 2 sensors mounted right where the air goes into the engine on the intake manifold, after the clean/dirty mixer pipe. They are air pressure, and temperature. These 2 are the most important for determining the correct pressure, and the rest are just compensation for climbing hills to help fuel economy slightly.

The IMAP Sensor...

The air sensor on the intake manifold is referred to as the 'IMAP sensor' or 'Intake Manifold Air Pressure' sensor. This sensor is in the path of both the clean and dirty air exposing it to soot on a constant basis. It is going to get dirty, start reading incorrectly, and will eventually fail, even on trucks that never idle, were soot problems are less. It is very easy to remove and clean (or replace if needed), so I recommend that you learn to do it yourself. I have seen service shops rebuild and/or replace entire turbo's, EGR Valves, etc. spending thousands upon thousands of dollars, trying to fix turbo-related fuel economy problems, never solving them, all because that sensor, along with others, are simply dirty. If you are ever faced with EGR related problems (Not DPF problems), where the turbo starts to act up as well, this could be a clean air related issue, but since the ECM relies on both clean and dirty air system to operate correctly, both should be looked at. Preventative maintenance to both these systems will always prevent major shutdown issues, so if you find, suddenly you are faced with EGR and/or DPF problems, just go through both the entire systems as throughly as possible. If you are not afraid to get dirty (and you shouldn't be if you want to be profitable), then start by performing an EGR Tune-Up. Most trucks have a way to display fault codes in some form or another, so make some phone calls or look on the Internet on how to do this. It usually involves turning the ignition switch and holding some buttons, writing down flash codes, then looking them up in some manual or reference guide. Call a repair shop familiar with your model truck, and verify your codes, getting some basic opinion as well. Turbo actuator, turbo speed, and/or intake sensor errors are definitely clean air related.

Before running off to a repair shop...

No matter what kind of EGR problems you may be getting, the first thing you want to do is go through the basics as much as possible yourself, before resorting to putting it in a shop. This saves you a lot of money and reduces the possibilities of the problem greatly. Next, if you have to go to a shop, have them perform the things you cannot do yourself as either a start, or as an addition to what needs to be done. Remember, you are paying them, make them work for their money in a way that ensures you get the most bang out of your dollars spent, so that your overall profitability, and fuel economy stays as high as possible. To troubleshoot and/or PM the clean air side of the system, start by doing the obvious. Replace the air cleaner for the engine if it is old, and check the piping between it, and the turbo for any cracks, gaps, and loose clamps or boots. If the engine will run at all, use a soapy water spray on all the intake piping, the turbo, the EGR piping, etc. looking for leaks while the truck is running. This helps eliminate the obvious like worn charge air cooler boots, and loose pipe connections. The next thing you can do, if you can do it yourself, will cost you no money, is to remove and inspect the IMAP sensor and/or the EGR mixing pipe and ensure it is not partially clogged with soot. As soot builds up in this pipe, your fuel economy indirectly goes down. The ECM will try to overcome this restriction by increasing exhaust back-pressure using the turbo. It is fairly easy to remove on most trucks, so doing this yourself will save you a lot of money. If it is dirty with soot, then just clean it out with a dry brush, like a tooth brush or a brush for cleaning cups when you wash dishes. Chemicals or sprays should be avoided, because they will usually turn this pipe into a soot magnet afterwards. The next cheapest thing you can do is just go ahead and pull and replace the the 'Intake Manifold Air Pressure Sensor', keeping the old one as a spare. It is less expensive than the other parts of the clean air system and a hundred bucks later, you will not only eliminate it from the equation, but ensure it is not costing you fuel economy from incorrect readings. If replacing it does nothing, clean up the old one using a dry toothbrish, and keep is as a spare for testing. Really, the only thing left in the clean air side of things is the charge air cooler, and the turbo itself. If it has been more than 200k miles since the charge air cooler has been tested, while the truck is down, definitely test it for leaks actually determining its 'leak rate', instead of just doing a pass/fail test. The leak rate should not be worse than 15 PSI of loss in two minutes. If it is, then it is costing you fuel economy, and if it is really bad, then it is a good bet that it was the initial cause of your EGR problems, but I wouldn't stop there. If your truck has 400k+ miles on it, The turbo itself can sometimes have actuator or bearing problems. These type of problems will usually result in faults to the turbo, but you have to be careful dealing with turbo faults. Many times, turbo or actuator faults can be caused by other sensors on the engine telling the turbo to go somewhere it cannot. The best thing to do if your getting turbo/actuator alarms is to replace the IMAP, and other inexpensive sensors before resorting to such measures. Removing the pipe between the turbo and the Charge Air Cooler, checking for internal oil leaks, etc. is always a good place to start if you suspect a turbo.

The Dirty Air...

The Dirty air side of the system, otherwise known as the EGR system, is a system that will always require some routine maintenance if you want to keep your truck at its highest fuel efficiency and ensure it does not have EGR problems. It is a good idea to understand this side of the system well, so that you can keep an eye on, and prevent problems before they shut you down. As the engine runs and produces exhaust, the exhaust flows from the engine block through the exhaust manifold, then branches off into two directions. Most of the exhaust flows into the back of the turbo, keeping it spinning, then out, past a short section of pipe where the dosing (after-treatment) injector is located, then down to your DPF. If your truck has no no DPF, then there will be no after-treatment injector, or DPF, but instead, an actual muffler. From there it goes out to the stack. Back at the exhaust manifold, where the exhaust goes two directions, the gas that isn't flowing into the back of the turbo, passes through several EGR components. Which device it passes through first, second etc. may be different on different trucks, but they all have the same basic components. The exhaust gas is 570 degrees plus, and is too hot to send back into the intake of the engine, so it is pushed through a small radiator called the EGR cooler to cool it off to about 200 degrees Fahrenheit. After that, it passes through the EGR valve, so that the ECM can control how much gets sent to the intake. After the EGR valve, it passes through a pipe that goes around the engine back to the intake, and along this pipe are 2 sensors. One is a temperature sensor, letting the ECM know that the gas isn't too hot for the intake, and the other is a sensor that detects how fast the gas is moving through the pipe. That sensor is called the 'EGR differential Pressure Sensor', or EGR 'Delta-P' sensor. This sensor is what the ECM uses to control the EGR valve to help get the desired clean to dirty air mixture. From there, the gas flows into the EGR mixing pipe, then the mixed clean and dirty air that goes into the engine.

Soot, Soot, and More Soot...

The 'Dirty Air' (EGR) side of the system is just that. It is very hot and contains soot, possibly coolant, already burnt fuel, soot, carbon dioxide, soot, NOX gases, and more soot. Soot is the killer of the entire EGR and intake system. Second to that is the possibility of coolant. Yes, coolant. Those hot gases are cooled off by the EGR cooler, which uses coolant from the radiator to do its job. If there is any kind of leak in the EGR cooler, then coolant ends up in the dirty air system clogging and sticking to everything, gumming it up and making it a soot magnet. Coolant also ends up in your cylinders where it gets pushed past the piston rings, getting into your oil, and destroying the oil's ability to lubricate your engine. An EGR cooler leak can destroy a lot of components fast, and can cause really big problems with every single exhaust related component including the turbo, all the sensors, the EGR valve, and the DPF. The signs of an EGR cooler leak are white smoke out the stack, a drop in coolant level where you can find no leaks, and/or failing a radiator pressure test where there is no leaks found. If the leak is small, then you can use 'Valvoline ZEREX Super Sealer for HD Applications ' to stop it, and is actually recommended by the engine makers for EGR cooler leaks. Using the super sealer is ok as long as you keep a close eye on your coolant levels to make sure it actually stopped the leak, but if it is a bad leak (you are going through a gallon or more of coolant in a month), then get it fixed right away. That much coolant can kill your DPF, EGR valve, or turbo very quickly. A total EGR cooler failure with a massive leak can actually hydra-lock your engine, so if your EGR cooler starts leaking, Personally, I would just replace it. Soot is the slow silent killer of EGR system components. No matter how you drive your truck, soot will build up in all the EGR components making them operate incorrectly, eventually causing them to fail. Idling an EGR truck can accelerate this process greatly, so if you have to idle a lot, consider getting an APU.

Isn't the DPF supposed to take care of the soot?,.. Can't I just do a Parked
Regen to fix it?,...

NO, you cannot do a Parked Regen to fix your soot problems, because NO, the DPF does not filter the exhaust sent to your EGR system. The act of mixing clean air with dirty air itself produces soot. That soot is carried by the exhaust gases from your exhaust manifold directly into your EGR cooler, EGR valve, Differential Pressure Sensor, Mixing Pipe, the Intake Manifold Pressure Sensor, and the cylinders. It deposits slowly over time, clogging them up, causing delayed readings, and eventually false readings and/or a stuck EGR valve. How fast this happens is relevant to the year of your truck, how much you idle your truck, how healthy the engine and intake system itself is. For most 2004 – 2006 trucks, the symptoms of soot related problems usually start at around 450+k miles. On 2007 - 2011 engines that do not use Diesel Exhaust Fluid, the symptoms usually start showing up at around 250-300k miles because they use more EGR than previous year model trucks, because of newer emission standards.

How does an EGR cooler get damaged and start leaking coolant?

Well actually the EGR cooler itself has no moving parts. This means there is nothing to wear out, so how does it break? By excess coolant pressure, corrosion from the coolant itself, or mechanical stress. Excess coolant pressure can damage it easily. If your radiator pressure cap goes bad, and it allows too much pressure to build up in the radiator, then very easily, it can crack the EGR cooler causing it to fail. A pressure cap is ten bucks, so I recommend just replacing it at the first sign of an EGR cooler failure, or if the EGR cooler actually gets replaced, just as a safety measure. Corrosion from the coolant is less likely, but possible. Regular testing of the PH balance of the coolant will usually catch this long before damage is done. A radiator flush and the coolant replaced at 400 – 500k miles is not just a suggestion, but very important to help keep the corrosive properties down. Lastly, and usually the most likely cause of an EGR cooler failure is mechanical stress. Some coolers are pretty delicate in their design, so excess stress can kill one fast. Excess stress can come from several sources, so all must be looked at when replacing a cooler. Excess vibration from the crank shaft damper is one source. They start to go bad at roughly 500-600k miles, so there again, preventative maintenance can stop this from being the source. Any time the coolant or engine overheats, it can cause excess stress in the form of rapid expansion to the cooler. This can come from actual overheating issues, or also from simply turning the engine off before letting the heat settle down after a long hill climb.If your EGR cooler is mounted directly to the engine block (most are), then any stress to the engine block itself, like rapid heating or cooling can cause the EGR cooler to crack under stress as well. The exhaust side of diesel engine blocks actually warp and distort slightly, settling over time. Most of this settling happens within the first 200k miles of the engine's life, but can happen again if the trucks operation is changed drastically. One example of this is a truck that has had its first 200+k miles spent governed at 63 mph, then suddenly it gets changed to 75 mph. The extra strain the engine is put through after suddenly changing its speed can, in fact, cause the engine components, including the block to have to 'settle' again. The engine is made of metal, not stone. Things settle, warp, and distort over time. The best way to avoid EGR cooler problems related to stress, is just simply to drive the truck in a reasonable manner, rather that to push it to its limits all the time.

Why do EGR valves fail?

Heat and/or soot mostly, but they can also fail from road salt intrusion. On many of the earlier EGR engines, and even on a few new ones, the exhaust gas from the manifold is sent into the EGR valve before it is cooled by the EGR cooler. This means that the EGR valve suffers the full 570+ degree heat from the exhaust. Poor design if you ask me, but I am not an engine maker. The engines where the heat is this high going into the EGR valve, generally suffer regular EGR valve failure problems, especially if they are driven hard. If you have one of these engines where the EGR valve is BEFORE the EGR cooler, then at first sign of EGR problems, have this valve re-tested, removed and cleaned, and/or replaced. The lifespan is usually about 200-400k miles on those engines.

On engines where the EGR valve is AFTER the EGR cooler, the exhaust gas temperature is only about 200 degrees or so. The biggest killer for EGR valves of this type of setup is actually soot and/or road salt intrusion. Soot will build up in the valve, eventually clogging it and making it stick. The problems with clogging and sticking are usually problems that produce no fault codes for the engine, unless they become very bad. What happens long before the fault codes, is that you get fuel economy loss, and/or turbo actuator problems. The turbo actuator problems are usually a ghost of the real problem, which is improper clean/dirty air mixture. Also, the turbo may get a symptom known as 'Turbo Coughing', where the turbo hesitates or spins up erratically. EGR valves that are sticky, can usually be cleaned instead of replaced, if done properly. Using chemicals to clean them is not a good idea, so a dry toothbrush, there again can solve some otherwise, pretty expensive problems. If you are unsure of your EGR and/or turbo problems, I recommend doing things from the cheapest and easiest, working toward the more expensive. The EGR differential pressure sensor, and the EGR mixing tube are going to get just as dirty, so start there. Replace the EGR differential pressure sensor and clean the EGR mixing pipe, and the EGR temperature sensor before even considering replacing the EGR valve. The next step is to clean the EGR valve to see if the problem changes or goes away. Replacing the EGR valve should only be done if it is actually the only thing left to blame for problems in the dirty side of the system (keeping in mind the clean air side). They are usually $800+ dollars or more to completely replace.

Predicting and Preventing EGR related failures,...

Preventing and predicting ERG related problems can actually be done by performing preventative maintenance on the EGR components. Unfortunately, since no one wants to be bothered by pulling parts off your engine just to clean them, most will argue that you shouldn't bother until you get an actual problem. It is those same 'Most' that end up in the shop with several thousands in lost profit by being down and paying a shop to maybe, if they are lucky, find the problem. Learn to remove and clean the EGR and Clean air sensors, learn to remove, clean, and re-install your EGR valve. Learn how to replace the After-treatment injector yourself. Learn to remove and clean your EGR mixing pipe. All of these things combined, can be done in a few hours saving you literally thousands in prevented downtime and repair costs. Take your truck to a repair shop for things like an EGR cooler leak or turbo failure, Not for the minor things you can do yourself, especially if those things have to be done regularly. To put it all together, based on experience helping many truck owners improving their fuel economy and/or solving EGR problems that the shops just couldn't fix, you should perform what I call an 'EGR Tuneup' at regular intervals (every 250k miles), or if you start to see the symptoms of an EGR problem. Information, including videos on how to perform an 'EGR Tune-Up' can be found here...

Fixing your EGR/DPF Problems...

This 'EGR Tuneup' should consist of the following...

• Remove, Clean, and Inspect These Components...

◦ Intake Manifold Pressure Sensor.

◦ Intake Manifold Temperature Sensor.

◦ Gas Recirculation Temperature Sensor (EGR temperature sensor).

◦ Exhaust Manifold Back Pressure Sensor.

◦ EGR Valve.

◦ EGR Mixing Pipe (Venturi Pipe).

• Perform These Tests...

◦ A coolant pressure test, checking for EGR cooler leaks.

◦ An oil analysis checking for excess soot and coolant intrusion.

◦ Charge Air Cooler Leak Test.

◦ Intake, Exhaust, and EGR Piping Leak Test (spray joints with soapy water during idling while pipes are not yet hot).

◦ Check turbo actuator for correct travel distance.

◦ Remove the exhaust pipe from front of the DPF, rev the engine, and check for excess soot from the engine during high idle and/or acceleration.

◦ A forced Regen verifying the temperatures and hpa readings.

• Replace These Components...

◦ EGR Differential Pressure Sensor.

◦ Clean or Replace the After-treatment Injector (If you have a DPF).

What about the possibilities of removing or disabling the EGR?,...

Well, it is illegal in the USA and several other countries. In the US, the EPA and/or CARB can fine you or shut you down. At some point, just like on cars, emission testing will get popular, as it will become another means of collecting money from the trucking industry. Keeping that in mind, the answer is Yes, but with possible consequences. Disabling your EGR on the newer engines can be done in 2 ways. Each of these two ways comes with its own set of complications and risks. Disabling it can be done by means of an 'EGR Delete', or by defeating it yourself.

An 'EGR Delete' can be performed by a non-OEM shop and can cost you as much as $8,000 or more. An EGR delete will allow the complete removal the EGR and DPF systems, but most of these after-market deletes and delete companies are terrible at actual ECM re-programming. It seems that delete companies with the biggest names in the industry are the worst at ECM tuning and re-programming too. If you own an ISX, the rick is the highest, as it is an engine that is very tricky to get right. Nonetheless, what takes place, is that cover plates are installed where the components used to be, a muffler replaces the DPF, and the ECM is reprogrammed for no egr. If done right, the benefits are high, such as longer engine life, significantly improved fuel mileage, and no more EGR/DPF related downtime, maintenance, or repairs.

One of the downsides is that if you live in the US and do this, and the EPA or CARB sees that this has been done, you can easily be faced huge fines and be shut down until it is put back to OEM standards. Another downside is that you not be able to take your truck to just any dealer or OEM engine shop. This is because by EPA law, all repair shops are required put the enigne back to factory, or face the same fines. Despite these downsides, there are many truck owners who take the risk and have it done. This is mainly because they are faced with going to extreme measures due to repeating failures. For them, the alternative, is to end up going out of business. Understanding your EGR system and performing EGR Tune-Ups will almost always avoid this completely, so the choice is really a matter of educating yourself. For more info on EGR Deletes, you can follow this link,...

ISX EGR Deletes -- Educate yourself...

Defeating your EGR yourself can improve your fuel economy almost as much as an EGR Delete, and has much lower EPA and CARB consequences because it can be undone very easily. It usually involves performing some voodoo engine sequence along with disconnecting your EGR valve and/or some sensor(s). The benefit is improved engine life and fuel economy, amusing it does not cause your DPF to malfunction or stop its ability to Regen. If your truck does not have a DPF, or it does not effect your Regen or DPF system, then defeating it is definitely a viable option, but not without taking a few other serious precautions. Knowing how the ECM is going to react and monitoring your exhaust temperatures while driving is the key to actually getting the benefits without risking a serious turbo or EGR cooler failure. With the EGR disabled, that 570 degree 'sweet spot' exhaust temperature is no longer maintained. The engine will run on only clean air, allowing the fuel to burn very hot, improving its efficiency

and reducing soot. Exhaust temps can easily reach 1300+ degrees, especially if you are climbing a hill. These much higher exhaust temps will have to be monitored while driving to prevent excess heat buildup on your EGR cooler and your turbo. It is not that difficult, but will require you to install a 'Pyro' gauge in your dash. I recommend putting the sensor right on the outside of exhaust manifold, near the turbo using a pipe or hose clamp rather than actually drilling a hole into your exhaust and putting it inside. What needs to be monitored is the heat buildup, not the actual exhaust temp. Just as a reference, I found a reference once, stating that the newer holset turbo can withstand exhaust temps of 1350 Fahrenheit for a period of up to 3 minutes. This means that the casing and/or your exhaust manifold can get to roughly 850 degrees without damaging the turbo. The next thing you will need to know is how the ECM is going to react to all this. First, the ECM is going to complain by turning on your engine warning light. With the warning light on all the time, you will have to keep a close eye on your fluid levels and other things to ensure you don't get an unexpected engine shutdown alarm. Assuming your engine is not already derated by the disconnected components, since your exhaust temps can get so much higher, you need to know that your ECM will limit your torque if you try to climb a hill with your foot all the way on the floor and the exhaust gets upwards of 1300 degrees. This is to protect your turbo, and is counterproductive to saving you fuel. That is another reason why you need to keep your manifold temp below 800 degrees yourself, so that you do not run into this problem.

Summing it up, Disconnecting your EGR will cost you the price of a Pyro gauge for monitoring the temp of the exhaust manifold. It will also force you to drive up hills in the correct gear for maximum fuel efficiency, keeping exhaust temps to a minimum. On really long gradual hills, you may on occasion, need to down shift a gear and use a higher rpm if your Pyro gauge reaches 800. Always, before shutting off your engine, you will need to glance at your Pyro gauge to ensure your manifold temp is below 500 degrees (400 is recommended). If it is not, then you will have to idle a few minutes to let it cool. This protects your turbo bearings and protects your EGR cooler. Like I say, not impossible to live with, but sometimes annoying. Is it worth it? Personally, I think so because even without the EGR disconnected, you should be driving efficiently and allowing your engine to cool before shutting it down anyways.

The DPF...

If your truck is 2007 or newer, it has a Diesel Particulate Filter (DPF), a Diesel Oxidation Catalyst (DOC), and a Dosing Injector (After-treatment Injector). All of it combined is referred to as the Exhaust Aftertreatment System.

This system is in place to further reduce emissions and to catch all the soot produced by an EGR engine. The After-treatment system itself is NOT part of the EGR system on most trucks, so this means that DPF and/or Regen alarms will usually only occur if the DPF system itself is unable to function properly due to, a problem within itself, coolant intrusion from a bad EGR cooler, excess soot problems with the engine, a cracked head, or if it has been disabled by the ECM because of a safety related engine issue like excess engine temp, fuel leaks, excess oil temp, excess fuel temperatures, or bad DPF sensor readings. Other EGR or engine related issues will not generally cause Regen problems if the After-treatment system is able to function normally, unless they are severe. Excess soot caused by an engine problem can very well cause the DPF to clog up, but only if the problem is fairly significant. If you, or the repair shop suspects this, then it can usually checked by disconnecting the exhaust pipe from the DPF and looking to see how much black smoke comes out when the engine is revved up high. A small to medium puff of soot is normal when the fuel pedal is pressed suddenly, but constant, or large amounts of soot can in fact cause problems. An oil sample from the engine can also reveal excess soot problems as well, so it is a good idea to do an oil analysis, checking for excess soot and coolant intrusion, when trying to solve DPF issues. The DPF itself is only part of that 'can' that looks like a big muffler under your truck. The front part of that can is actually the DOC. The DPF is nothing more than a ceramic 'soot catcher'. Yes, it is made of ceramic similar to the honey-comb of a bee hive. Smacking the outside of it with a hammer to loosen the soot, or if road debris hits it, then it will crack that rather expensive, difficult to manufacture honey comb brick. Attached to each end of it are 2 small stainless tubes going to a sensor known as the DPF Differential Pressure Sensor. That sensor tells the ECM how clogged up this soot catcher is. Also, there are 2 or sometimes 3 Temperature sensors to monitor how hot the exhaust is going in and out.

The DOC...

The Diesel Oxidation Catalyst (DOC) is attached to the front of the DPF inside the exhaust can. It is the diesel engine equivalent to a Catalytic Converter on a car. It converts harmful exhaust gases into less harmful ones and has an optimum or 'sweet spot' temperature that makes it work efficiently. Any more than 50 degrees above or below 570 Fahrenheit, and it doesn't function as well, so this is exactly why the EGR system on your engine tries to regulate the exhaust temperature at 570 degrees. A temperature sensor is usually mounted on it (sometimes also used as the DPF inlet temp sensor) to let the ECM know if the EGR system is doing its job. A Regen cycle does not remove the soot from your DOC, so if your DPF ever has to be removed and cleaned, then the DOC needs to be removed and cleaned as well so that it doesn't create a loss in fuel economy or get packed with soot.

The Doser Injector (After-treatment Injector)...

The After-treatment Injector is mounted directly behind the turbo and is really the only active component in the After-treatment System. It isn't like the engine injectors, but rather more similar to the spray nozzle of a hair spray can. During a Regen cycle it activates, spraying fuel into the exhaust pipe as a fine mist. If everything is working properly, the fuel accumulate on the face of the DPF and egnite there, and not inside the pipe, burning out the trapped soot the DPF has accumulated. The soot is converted into Carbon Dioxide and gets pushed out the exhaust stack. This injector is the key to keeping the after-treatment system functioning properly, but unfortunately, it is exposed to all the soot and other bad things that can end up in your exhaust pipe. It is not uncommon for this injector to start clogging up at around the 200-300k mileage on many trucks. After that, it is just a matter of time before you start to see those proverbial Regen Lights in your dash. Some of the engine makers suggest cleaning it every 200k miles, and this is good advice, but cleaning them usually involves shutting the truck down, draining the coolant, removing it, replacing the gasket(s), and if you are lucky, getting it clean enough to last another 200k miles. For a couple hundred bucks, I have always just recommended just replacing them. Removing it and replacing it is actually not difficult. There is a small coolant line that connects to it, so if you are going to tackle replacing it yourself, you will need a couple 5 gallon buckets to drain your coolant into first. Since it will be replaced more than once during the trucks lifespan, I recommend some high temperature anti-seize on the screws and fittings as well.

What exactly is a 'Regen'?

A Regen cycle is a cleaning cycle performed on your DPF to get rid of the excess soot that builds up in it. There are actually 3 basic types of Regens. They are Passive, Active, and Forced. A passive Regen is performed by your truck about every 350 – 400 miles depending on the make and model truck you have, whenever you are driving. There is usually no indication whatsoever that it is happening, and if you are not one to idle your truck very much, this passive Regen should be enough to always keep your DPF cleaned if everything is functioning properly. If you ever get a 'Parked Regen' light on your dash, and you don't idle your truck much, then it is a definite sign that it is time to take a close look or perhaps replace your after-treatment Injector. If that looks good, or is new, then you need to find out why the passive Regen cycle is being interrupted and/or delayed by your ECM. Not taking an active approach to this will definitely cause your truck to end up in a Derate, or worse, an engine shutdown, putting you in a shop for major repairs before it is over with. If you do idle your truck a lot, then an occasional Parked Regen light might be ok. In either case, I recommend holding off on actually doing a Parked Regen unless you have driven about 300 miles and it has not gone out. Your only short term solution if you are getting Parked Regen alarms that do not go away after you start driving, or if they return frequently, is to actually perform a Parked Regen, but to right away, have your after-treatment injector inspected and/or replaced and your EGR system tuned up as soon as you can. Since you now know that your truck will do a 'Passive Regen' every 350 miles or so, getting a Derate or DPF warning every 350 miles will clearly indicate there is a problem in your After-treatment system.

A 'Parked Regen' is the truck's way of forcing you to manually Regen your after-treatment system to clean it because the Passive Regen in unable to keep up. If your Injector is good, and there are no cracks or gaps in the exhaust system, then a Passive Regen is more than enough to keep the system clean. This means that Parked Regen warnings or requests are actually your first sign that things aren't quite right. Also this means that you are loosing fuel economy from the restriction of soot in your DPF. A Parked Regen will usually take a while to complete, even on a healthy DPF system. The reason is that the truck needs to raise the temperature of the DPF to above 500 degrees before fuel injection can take place, then performing several sets of pre-programmed cycles. On the ISX, this is a minimum of 40 minutes. The temperature of the DPF should reach 1,000 degrees Fahrenheit+ when this is happening, but the outside temperature of the DPF will usually be lower because of insulation. How long it takes to perform this Regen is also totally dependent on how fast it can get the DPF to reach these temperatures. If your truck takes more than 1 hour, then there is definitely something wrong.

A 'Forced Regen' can be done by the driver on some trucks, but not always. This type of Regen is a last resort effort to remove soot from the DPF when there are other things wrong. If your engine has disabled the Regen system because of another fault (like excess fuel temperature), then a Forced Regen may get you rolling again temporarily, but your problems will likely return in 300-400 miles when the Passive Regen fails again. It is quite often that repair shops will blame your truck problems on just simply the fact that your truck needed a 'Forced Regen'. NOTHING CAN BE FURTHER FROM THE TRUTH!. Don't be fooled by this. You ARE going to end up in the shop again in a very short order. If a Forced Regen has to be performed, then something else is very wrong. The entire EGR and DPF system will need a thorough looking at, starting with the after-treatment injector and/or EGR cooler. Your DPF can in fact get clogged with ash itself, but that usually takes 600+k miles or more to happen. Removing the DPF itself and having it cleaned should be as a last resort item only after performing a Forced Regen using a new injector. Simply removing the DPF can cause it to crack its ceramic interior, costing you thousands for a new one.


Problems with 'Selective Catalytic Reduction' (SCR)/DEF (Diesel Exhaust Fluid) systems are many. Personally, I have never owned a truck with one of these systems, so I cannot elaborate on them too much, but I do know that the fluid itself likes to crystallize and clog up the components. Keeping the DEF tank full, keeping the cap clean, and spare DEF tank and SCR unit filters on hand will reduce these problems by quite a bit. Replacing filters and/or getting the injector cleaned regularly is probably a good idea.


With any of these systems, using some common sense, thinking pro-actively will help you stay on top of almost all problems that are likely to occur. Taking the time to understand and perform basic maintenence and rapairs yourself will definitely save you thousands upon thousands in repair bills and down time. Stay well informed, and get the correct information for your particular truck. Your extra efforts will be always rewarded in the money you save. it may well make the difference between taking home a profit with your truck, and loosing your butt. Be a Truck Owner, not a truck driver. Get on top of your problems, and get dirty. It will reward you in return.

{12-19-2017} - I found this great video on DPF system woes...

User's Signature: ->: What I post is just my own thoughts and Opinions! --- I AM Full Of S__T!.
 Thanks given by: scottydogtruck , Bubblewrap , walterk
12-06-2017, (Subject: Understanding Your EGR and DPF as a Truck Owner ) 
Post: #2
RE: Understanding Your EGR and DPF as a Truck Owner
How do I the info on the @m*m^2 tune
 Thanks given by: Truckerheerde
12-07-2017, (Subject: Understanding Your EGR and DPF as a Truck Owner ) 
Post: #3
RE: Understanding Your EGR and DPF as a Truck Owner
(12-06-2017 )Smoothshifter99 Wrote:  How do I the info on the @m*m^2 tune

Assuming you live in a country that allows such things.... You should likely get in touch with Mr. Hag, Gearhead, and.or Unilevers if your looking to get some of that type of work done.

User's Signature: ->: What I post is just my own thoughts and Opinions! --- I AM Full Of S__T!.

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