Entering the diesel realm with a 3rd generation Cummins 5.9L marks a promising journey. Renowned for their robustness and upgrade potential, these engines stand as solid choices in the diesel community. While the 12-valve variants are esteemed for their power-handling capabilities, the 24-valve models boast superior horsepower and fortified internals, setting the stage for impressive performance upgrades.
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Explore custom tuning options and unleash the full potential of your Cummins engine with Schultz Diesel Sports.
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A diesel truck – especially one with a Duramax engine – is a big investment, and you want to take care of it. So, if you get a scan and it comes back with a trouble code, it pays to know what’s going on under the hood.

One of the most common DTCs (diagnostic trouble codes) for Duramax trucks is P003A. Here’s what you need to know if you encounter it, and the steps you should follow to fix it

When your mechanic or code reader has scanned your truck’s engine computer, DTC P003A is one of the possible errors that can come back. Obviously, that doesn’t mean much to someone unfamiliar with the scanner!

The technical definition of this DTC is that “the turbo charger/super charger boost control A position has exceeded the learning limit.” In plainer terms, this means that the variable geometry turbo (VGT) turbine vanes cannot move from 0% (open) to 100% (closed) fast enough.

So, now you’re likely asking: what are turbine vanes?

Well, these are what enable the turbo to change its efficiencies throughout the engines RPM range. At a low RPM, they allow it to act much smaller and function as a small, quick-spooling turbo. At a high RPM, they allow it to act much larger and provide more top end power.

The vanes are what regulate air through the exhaust side(or better known as the turbine) of the turbo, where it can start spinning the turbine. At lower RPMs, the vanes will close up to 100%, letting only small amounts of air through – but because of the small opening, the air pressure rises and causes it to move faster. This starts spinning the turbine.

Then, as engine RPM and power increase, the vanes open up more and more from that initial 100% closed position. They can go all the way to a 0% closed (in other words, wide open) position, depending on how much boost pressure your truck requires. Though they were originally designed for emissions purposes, the after-market has embraced this design to maximize the narrow power band that a diesel engine operates in.

Every time your engine starts up, the engine control module (ECM) performs a process known as a turbo vane position learn. Essentially, this means the computer tells the turbo to close the vanes to a point between 0% and 100%, and periodically throughout your drive, it will repeat the process.

The computer uses engine oil pressure to cycle the vanes from 0-100%. This pressure pushes a plunger, which moves the unison ring and, in turn, cycles the vanes through their whole range from closed to open. In a P003A code, the problem lies with the unison ring: it seizes up and can no longer turn its full motion. This is generally caused by rust on the turbo cartridge, which stops the ring and causes the turbine vanes to “stick”

In everyday driving, the vanes function almost entirely between the 20%-90% range. When the ECM does a periodic vane position learn, it makes them open from 0% to 100%, and these outer limits are where the vanes become stuck or slow to respond.

After-market tuning can exaggerate a sticky vane issue, because when trying to exhaust brake (100%) or “rumble idle” (0-20%), the turbo is being sent beyond its “worn-in” range. The coolant temperature and length of idle will also affect the performance, because when the engine is cold, oil pressure is high and more force will be put onto the plunger and unison ring. This often forces the vanes through the stuck positions. However, as engine oil temperature increases, oil pressure drops and it no longer has enough pressure to work through the rusted portions

The main mistake involved in this DTC is assuming that the vane position sensor is faulty. As we know, it’s almost always the unison ring getting stuck, which prevents the sensor from seeing what is happening. The sensor reads correctly, but the ring is physically stuck and cannot push the vanes to the proper places that the ECM is asking for.

These sensors rarely fail and are easy to test when removed from the turbo, which means it’s simple to ensure they are not the problem. Beyond that, the best way to diagnose a sticking unison ring is with a scan tool that can command a vane position.

To do this procedure, you should cycle the vanes from 0% to 100% while the engine is hot. If the ring is working properly, this vane sweep should be completed within 1 second. If it takes more time than that, or there is a slow response on either end of the position, it’s likely that the unison ring is getting caught up on a rusted turbo cartridge

For a temporary fix, it’s possible to remove the turbo, split it apart, and remove the rust on the cartridge where it meets the unison ring. This may give you a few more years of service, but remember – if it rusted once, it is basically guaranteed to rust again. The permanent fix is to replace the turbo with a new unit with additional “pins” installed in the cartridge. These pins help clean the unison ring and promote a longer life of the components

Here at Schultz Diesel Sports, all new turbos have these scrapers installed to ensure you get many years of great service. If you’re getting the DTC P003A reading on your Duramax truck, reach out and let us know – we’ll have it running like new in no time

As diesel lovers, it doesn’t get much better than a Duramax – but it seems like they all suffer from one common problem: head gasket failures. We get a lot of questions about this topic, so here we’ll talk about some of the most frequent ones, give some insight on the repair process, and outline some issues that may need attention while those repairs are going on.
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Let’s start with the biggest question: why do head gaskets fail?


Well, throughout the years, GM has revised their head gasket design multiple times and they each fail in their own unique way. No matter which gasket design your Duramax has, they are all susceptible to overheating – the #1 reason for failure.


Gaskets live a very hard life, in a harsh environment that deals with extreme temperature and pressure changes. These extremes mean that, in general, they are the first major engine component to fail – not only on a Duramax, but on most diesel vehicles.
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There is no real clear-cut answer for this question, which is often asked by new diesel owners. All we can really say is that it is typically the first major component to fail. However, there are some trends, based on the year the vehicle was manufactured.
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The most common concern with blown head gaskets is the loss of engine coolant with no apparent visual leak.


When the gasket fails, the general problem is that cylinder pressure leaks into the cooling passage, over-pressurizing the cooling system and in turn pushing coolant out of the reservoir when it comes under heavy load. These trucks will start and idle without any smoke, and there can be no visual coolant loss, but the driver will have to constantly put more coolant into the system. 


Many people think that they need to put in more coolant only when they are towing – because they are working the engine harder, putting more pressure into the cooling system, and the leaks occur while the truck is driving (and they don’t see the leak).


The 2006-2010 riveted gaskets are the only ones that don’t follow this pattern, because they do leak externally when they fail and rarely cause this over-pressurization. However, these will often have coolant puddles on the ground when the truck is parked overnight, making it easy to see that there is an issue.


Another good indicator of failed head gaskets is a “stiff” upper rad hose. If there are no external leaks, the cooling system can hold excessive pressure for months after the engine has been shut off. A simple test is to put the engine under a good load at operating temperature, then shut it down and let the engine cool off for 8 hours or more. If the upper rad hose is still firm and opening the coolant reservoir cap releases air and pressure, the head gaskets have almost certainly failed.


The last common indicator is constant coolant leaks. With the added pressure of failed gaskets, people may find they are constantly chasing coolant leaks – a never-ending battle of replacing water pumps or coolant lines and tightening clamps. When trucks roll into our shop for a basic water pump job, it’s common to find a failed head gasket on the truck.
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This is a common misconception about the grades of head gaskets. GM has 4 different grades, A, B, C, and D, which are used to signify the dimensions of the gasket – and Grade C is the thickest factory-installed gasket. This means you can get a Grade C gasket in the 2001-2005 crimped style, the 2006-2010 riveted style, and the 2011-2016 gold colour.


The grading has no bearing on whether the gasket is good or bad, only on its thickness. In our opinion, the best gasket is the 2006-2010 riveted design, and it’s the only one we use on all of our head gasket repairs and engine builds, from stock to high horsepower competition engines. 
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This question comes up all the time, and the truth is this: it is rarely the head bolts that cause the failure of the Duramax head gasket.


A Duramax is not a 6.0 Powerstroke, and the factory GM bolts are more than adequate. When we perform these head gasket jobs at the shop, we will warranty head bolts to 700WHP, far surpassing the “safe limit” of the factory pistons and connecting rods in a Duramax diesel. With head studs costing $900+ CDN and head bolts coming in under $200, we believe most customers that use their trucks for work , towing, or casual racing with mild to modest performance upgrades, could better spend that money on other upgrades.
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When we are performing a head gasket replacement, we must take apart the entire top end of the engine. This makes it a very good time to think about other performance upgrades, because there are little to no additional labour costs to do a lot of engine modifications.


For example, it can take 8-16 hours to remove the exhaust manifolds, up pipes, turbos, fuel injectors, and injections pumps. While we are there, we like to do any requested upgrades in that area of the engine. Depending on your end goals with the truck’s performance (and your overall budget), replacing gaskets and installing modifications are perfect to do together.
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A hard question, but it’s necessary to know! With the amount of teardown and rebuilding required in order to do the job correctly, it will take 36-44 hours to complete – there’s no other shortcuts to take. We recommend putting rebuilt heads on all trucks with mileage above 250,000 km because of worn valve guides. All in, the average cost is around $7,500 - $8,500. 
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If you have the skills, sure – it is a large and complicated task, but it does come down to just nuts and bolts.  Our recommendation is that you stay well-organized, have a spacious and clean work area, and clear out your schedule, because you’ll need a lot of spare time.


We have entire gasket packages on our shelf to get you everything you need to do the job correctly. Even pros like us started in our home garages, and we know the thrill of getting things done DIY-style, so feel free to tackle the project – and if you need any help to finish it off, you know where to find us!

For a lot of people, the inner workings of an engine are a mystery – and so is the ability to peer under a hood and get an idea of what’s going on. But the days when our grizzled old grandpa could remove a transmission, fix it up, and replace it are long gone, thanks to the rise of electronics that monitor and adapt to how an engine runs. This is especially common now in diesel engines.
 
Today’s transmissions are much more complex than they used to be. A few decades ago, transmissions were commonly only 3-4  speeds, so while they did require some training to understand, they weren’t a complete mystery. Now, though, you can easily find 6-, 7-, or even 10-speed transmissions, each of which adds a layer of mechanical complexity. In addition, the role of electronic management in the engine has grown, too – so now overlaid on any transmission is a “smart” computer system, capable of adaptive learning using the data it collects while you drive.

Far from saying anything about your driving style, the adaptive learning process is actually quite a benefit to your transmission as a whole. It decreases wear on the entire drivetrain, increases the lifespan of the internal moving parts in your transmission, boosts your fuel economy and performance, and overall just makes your driving experience better. It will help shifts be smoother and nearly unnoticeable during quick trips to the grocery store, but also ensures you have the best power and confident shifts possible when hauling trailers out for weekend camping trips. Put simply, it creates an optimal gear shift, in any situation.

Built into a new engine are multiple sensors, for collecting data on things like throttle position, fuel pressure, mass airflow readings, and so on. The transmission control module (TCM), part of the electronic system of the vehicle, will adjust the timing of ongoing and offgoing clutches automatically, in conjunction with the pressure going to those clutches. This makes the shifts feel more smooth or more purposeful as needed.

TuningWe can see that Cylinder 6 has a huge compression loss issue, from something mechanical going on, and the truck is running that cylinder at 25.5 mm³ (11 + 14.5), while the others are around 4-5 mm³. Even the high CFR itself, at 11 mm³, is often a sign of something going wrong – it’s common on engines with compression differences of this size, and may be mistaken for a bad injector. Further tests may be required to really get to the root of the problem.
 
At Schultz Diesel Sports, we strive to diagnose the engines we see, properly and quickly. We hope that this gives you some insight to the calculations behind balance rates, and how they work and what they mean – so that if you encounter trouble of this type, you know the background of the problem and how to identify it, too. That way, it can get fixed faster, and you’ll be back on the road enjoying your Duramax in no time.
 
A product that we recommend is Edge Insight. It shows you your balance numbers and your CFR in one easy-to-use display, which is why we sell them off the shelves and put them in our own trucks. Of course, there’s still a lot more to learn about diesel engines and all the science that goes along with keeping them running at their best – so if you ever have any questions about your Duramax balance rates or anything else to do with your truck, don’t hesitate to reach out to Schultz Diesel Sports... especially if it is about Diesel Truck Tuning!
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Can’t afford that brand-new, top-of-the-line diesel truck? We know how tempting it can be, and how hard it is to say no. But that doesn’t mean you can’t find something great out there that’s new to you. When you find that perfect vehicle that’s just within your budget, driving it home can feel like you just won the lottery.
 
But as with any lottery winning, you have to be careful that you don’t get more trouble than you anticipated. It’s no different with a used diesel vehicle – you don’t know if the engine looks good on the inside, if the parts are clean, or if the fluids are topped up. So why take the chance on breaking down before you even get a chance to really enjoy your new ride? Assuming you already know what to look for when buying a diesel truck... here are the top 4 things to do AFTER you buy a used diesel truck, to make sure you stay on the road and moving fast.

If you didn’t read our last blog on why the quality of diesel fuel is important, well, you should know that it really is. Diesel engine tolerances are very precise, so fuel that has contaminants or other low-grade particulates in it can ruin your whole system and set you back thousands of dollars. An easy way to avoid this? Change the fuel filter when you get a used truck. It doesn’t matter if the one already installed is the best brand on earth – you simply have to be sure that it’s brand new and can do its job effectively. It’s a good habit to change these with every second oil change, to keep your engine running smoothly.

​A lot of people aren’t aware of just how diesel engines work – or how precise the parts under the hood really are. While they operate, for all intents and purposes, on the same principle as gasoline engines, the demands of the components in a diesel system are much, much higher.
 
You may know that bad fuel filters and low fuel quality can be costly, but you probably didn’t think they could set you back $10,000 or more. It’s true – poor fuel can really wreak havoc on your entire engine! This is so important in diesel vehicles because of the extremely high tolerance points of each piece. For example, it's not uncommon for modern diesel engine fuel systems to produce upwards of 30,000 PSI; obviously, a pump, its fuel lines, and junction points that can handle this massive pressure have to be in optimal condition in order to operate.