Causes Of A Peterbilt Derate (and What You Can Do)

You may have been dealing with a problem concerning a Peterbilt derate. 

Now, this can definitely be worrisome since it reduces the performance and power of your engine. 

If you are worried about an engine derate with your Peterbilt, keep reading this article to learn more about what you can do about it. Let’s jump right into it.

peterbilt derate

What Is A Peterbilt Derate?

Basically, an engine derate is your vehicle’s self-protective feature. It limits the function of your engine, which comes pre-programmed right into your vehicle’s operating software. This is an advanced function that became quite popular in recent years. 

The idea behind a derate is quite similar to a limp-mode feature found in vehicles powered by gasoline. When you experience an engine derate, this limits the performance of your engine. The amount of power produced is just enough for you to pull over to a safe location and seek professional assistance for your vehicle’s issue. 

Now, the level of derate depends from one manufacturer to another. In the case of a Peterbilt, the derate can go to about 5 MPH, which is the case if you are unable to identify and resolve the issue quickly. This derate level can also be observed in some other Volvo trucks.

If you fail to do appropriate actions during the 5 MPH derate, then your vehicle may go into a shutdown that is induced by a derate. This will then impact your vehicle, requiring it to be towed for repair. 

There are also many manufacturers that disqualify some segments of their truck’s powertrain warranty when the derate level has already been reached previously. 

As for the reasons why an engine derate occurs, it could be due to a number of causes. For instance, it is often linked with the emissions system of your vehicle. These issues can range from the DEF quality and also the DPF and SCR catalyst efficiency errors. But overall, these faults can seriously impact your vehicle’s ability to perform and complete an automatic regen cycle.

Now, regen refers to the process of converting soot and other types of particulate matter that are stuck in your DPF into ash. This is completed by applying heat and some chemical compounds. The diesel exhaust fluid is introduced, as well, into your vehicle’s SCR catalyst for the purpose of reducing nitrous oxide emissions.

There are many sensors in your diesel engine that monitor the efficiency of these reactions. The most common of these sensors are the back-pressure, temperature, and the pressure differential sensors. If any of the sensors provide feedback that happens to be out of the specification, this leads to an engine derate.

But then again, an engine derate may also happen due to some self-protection functions under some additional criteria. However, the actual point at which this engine derate occurs depends from one vehicle manufacturer to another. 

There are trucks that enter into an engine derate when the oil or coolant levels drop at a certain level. It can also occur because of an overheating issue.

What You Can Do During A Peterbilt Derate

peterbilt derate

The thing is that the issue with engine derate is not always easy to address by any at-home mechanic or just about any average operator. Some derate conditions would need to be addressed and even reset using an OEM-specific diagnostic tool, which is not like the usual OBD2 scanner that you have.

Hence, you will need to visit a specialized service center to get your vehicle fixed, which is where such sophisticated software is available. There may also be some underlying issues with your engine, which need to be repaired to restore full power.

This is why some technicians will have to conduct a forced regen and then reset the derate status of your vehicle. But if the cause of the soot-loading excess is not identified easily and quickly, this can end up in a further derate.

Now, forced regen can be utilized in some instances just to buy some time before a more intensive derate process is performed. Although the features are not accessible unless you have a scan tool, there are some vehicles with a simple switch for activating a forced regen. This enables you to initiate a regen manually. However, you can only do this while parked and in a safe location. You should also be far away from other vehicles to prevent potential damage.

But no matter what the cause of an engine derate may be, it is absolutely critical to have the problem addressed sooner than later. This way, you can prevent more intense derate levels from being registered, which will also circumvent further damage to the engine. 

If you are not comfortable or confident about doing the necessary repairs by yourself, then you should make it a point to seek professional help. This way, you can get the problem addressed properly and get the result you want.

Wrap Up

A Peterbilt derate happens because of numerous reasons. It could be due to the emissions system, or the DPF and SCR catalyst efficiency errors. When these problems arise, an engine derate occurs. For issues linked with emissions, the vehicle is likely to get into a 5 PMH derate enabled by your ECU.

This can also happen at just about any time because the moment you lose connection or experience a sensor concern, then the derate will happen very quickly. With that being said, it is best to have the problem addressed appropriately by an expert who can provide favorable results and prevent the issue from getting worse. 

In some instances, you may be able to have the issue addressed yourself, as long as you have the right tools and skills. Otherwise, it would be good to visit your dealer and have them work on your vehicle’s engine derate issue once and for all.

2 thoughts on “Causes Of A Peterbilt Derate (and What You Can Do)”

  1. I need help with my 2018 Volvo D13 VNL64T, Spewing antifreeze out while climbing hills, have not had an oil change since I bought it last month, I did change the air filter its not suffocating anymore but still have to add 1/2 gallon of antifreeze everyday. 495,000 miles on the engine

    • Hi Bobbie,

      It sounds like your engine may be experiencing a coolant leak, which can cause overheating and ultimately lead to serious engine damage if left unresolved. Here are a few things you can check to diagnose and potentially fix the issue:

      – Make sure the coolant level is at the recommended level, and that there are no obvious leaks or damage to the coolant lines or radiator.

      – Look for any signs of damage or leaks on the radiator itself, including cracks or other visible signs of wear.

      – The water pump is responsible for circulating the coolant through the engine. If the water pump is damaged or malfunctioning, it can cause a coolant leak.

      – A blown head gasket can cause coolant to leak into the engine, leading to overheating and other issues. Look for signs of white smoke or a sweet, burnt smell coming from the engine, which can indicate a blown head gasket.

      – While changing the oil won’t fix the coolant leak, it’s important to keep up with regular maintenance to ensure the engine is running as efficiently as possible.

      It’s recommended that you take your vehicle to a certified mechanic for a thorough inspection and repair, as driving with a coolant leak can cause significant damage to the engine.

      Have a nice day!


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