What is Engine Derate? Everything You Need to Know

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engine derate

An engine derate means that the computer software controlling the car’s engine restricts the automobile’s power and speed. It is intended to safeguard you from inflicting harm to the engine. However, engine deterioration, referred to as derating, might be pretty advantageous in some circumstances. It enables a longer engine lifespan by reducing substantial wear and the chance of overheating.

Before the car’s check engine light illumination and the engine derating, the onboard system has taken many preset procedures to clear the Diesel Particulate Filter (DPF). Your vehicle’s monitoring system keeps track of the quantity of fuel that passes thru it, as well as the diesel particulate filter’s temperature and pressure.

A programmed formula then determines the actual limitation and the predicted DPF restriction. While cruising along the road, your engine is constantly working to clean its DPF system. When the DPF system is not effectively cleaned, the DPF light will illuminate, and you’ll be required to assist in the cleanup procedure.

You’ll then have two alternatives. You can choose to adjust the car’s operating mode to increase the amount of heat received from your exhaust system, or you may choose to park your car and execute an active regeneration. If nothing is done at this phase, a red stop engine light on your panel will activate, and your engine could ultimately shut off or derate.

What Is Engine Derate?

Engine derating is the process of modifying an engine so that it operates at a reduced capacity than its actual capability. The derating process can be done deliberately to minimize engine problems caused by excessive wearing, resulting in prolonged engine life.

That means you can derate your car’s engine to run at less than its maximum rated overall power. For instance, if you own a power supply generator, you can intentionally derate the engine to extend its lifespan. However, this results in a reduction in power production compared to its previous regular entire operation.

Engine derating is not limited to power generators or car engines; any equipment powered by a motor or machine can undergo the derating process. However, if you derate specific engines or machines, especially on a car, the vehicle speed or total engine performance will be reduced.

Derating is a procedure that is used to keep the engine against overheating. Each engine is intended to operate in a given setting, like the ambient temperature. Engine derating is conceived and built in a way that the derating of an engine starts when the surrounding temperature exceeds the engine’s typical working temperature.

When the surrounding temperature rises to 40°C, an engine intended to run at 30°C might lose 10% of its output power. This renders a lot of heat and decreases the engine’s efficiency. An additional impact of higher engine temperature is greater fuel consumption.

Three Different Ways Of Engine Derates

You should understand a few concepts regarding the engine in terms of engine derates. One of the concepts is comprehending these three distinct varieties of engine derating listed below.

Intentional Derate

Sometimes, engines are purposefully derated! An intentional derating happens when a consumer requests that the carmaker reduce the engine rating and capability. There are reasons why buyers desire this.

Each engine is built for specific and unique activities that might not always correspond with the manufacturer’s standard setups. Manufacturers might essentially adjust the preset parameters to get the desired outcome.

The key benefit is that the decreased thrust saves money and extends the lifespan of an engine. Another benefit is that it might enhance the optimum takeoff load for a particular track by employing a decreased thrust profile in particular conditions.


  • It is cost-effective in terms of engine care
  • Lengthens the duration of an engine’s operational mode


  • Low-speed performance

Unintentional Derate

Meanwhile, as previously said, unintentional derating is a much more severe and pressing matter. Whenever engines are derated, it is stated that they will deliver a specific level of power under specified circumstances. All promotional materials and marketing techniques take these parameters and longevity into account.

Typically, each engine is optimized for operation at a certain temperature and fuel. For instance, when the engine is utilized in the proper climate and is supplemented appropriately, it would survive better and be highly dependable. Otherwise, the engine won’t produce the equivalent power level and could have a shorter lifespan.

This is a significant source of consumer dissatisfaction since the suggested fuel and fluids are costly, and not all consumers can pay them. Over a couple of years, the engine starts to perform harder and produces lesser power than before, resulting in waste.


  • Shorter engine lifespan
  • Increased fuel consumption
  • Less engine performance
  • Expensive to renew a knocked-out engine.

5mph Engine Derate

Various sensors or systems trigger derating by 5mph in the car’s emission system. You must realize that the fault is associated with emissions if your engine derates by 5mph. To better understand the 5mph engine derates, familiarize yourself with the entire emission system’s components.


  • Dealers may resolve fault codes using the OTR Diagnostics and OTR Reset Tool. As a result, you can simply replace faulty or worn-out components. Additionally, you will get the opportunity to clear the check engine light (CEL.)
  • Rebooting 5mph DEF derates would be accomplished using the OTR Diagnostics and OTR Reset Tool. Additionally, you will save money and time by not having to take your vehicle to an auto repair shop; OTRs can transmit the resets straight to your dealer.

Emission System Components That Manages The 5MPH Derate

To adequately learn the 5MPH engine derating, you must first know the components making up the emission system. Below is the list of essential elements of the emission system that play a significant role in managing an engine’s 5mph derate.

DEF Doser Valve

Controls the DEF fluid injection through the SCR Catalyst.

DEF Fluids

DEF Fluids are contained in the tank or container with a blue cap. This device has a quality sensor and a leveling sensor to ensure that concentrations remain within permissible limits. However, a bad DEF fluid might affect the quality of your DEF and leave you in a derate state.

NOx Sensors

Suppose the sensor identifies a high amount of NOx inside the exhaust stream. In that case, it instructs the SCR/DEF system to infuse extra urea that utilizes ammonia to decrease emissions in the exhaust system.

DEF Pump Assembly

This is indeed the heart of the DEF system; it is responsible for pumping the DEF fluid constantly. If this malfunctions, you could instantly undergo a derate.


The ECM controls the DPF system and renewal process for the Cummins truck or vehicle. Thus, the DEF module and the ECM combine to manage the complete operation.

DEF Control Module

This module is in charge of the emission system’s functioning. The Engine Control Module (ECM) and DEF Module communicate directly to ensure that the system operates properly.

The Fault Code That Results In 5MPH Derate

  • The Cummins Fault Code – 3712 or SPN-5246-FMI-0  
  • Notification – Illuminated red “stop engine” warning light
  • Information – When you find out that a strict SCR fault code is activated for a long time, you must seek quick assistance!
  • Immediate Engine Derate – If the car’s top speed is restricted to only five miles

Engine Derate Fix

You might have become bored with your vehicle derating, and you want to repair it and restore regular functioning to the vessel; below are the list of a few fixing.

  1. Resolve the core issues and delete any fault codes that result in derating. Correcting the root issues will assist in completely removing derating fault codes.
  2. Restore the counter back to zero to assist the engine in restarting at its maximum performance.
  3. To restore regular confirmation functioning, reboot your engine 3 times.
  4. Suppose the repair confirmation fails, you will have to restart your engine within half an hour since it would have derated.
  5. Upon resolving that issue, restart your engine using an incentive counter and wait around half an hour. When no faults are detected throughout the period, the computer will restore regular functioning.


This article’s guide and instructions are not entirely necessary. This is primarily a diagnostic examination to see why the DPF system isn’t functioning perfectly and will start the regeneration process.

In the situation of a derate, it is crucial to seek out professional assistance. It is highly suggested that you pay more attention to the emission system when warning signals of impending derate appear.


How is engine derate calculated?

The derating factor of a generator is the highest capacity of a cofired generator running at the lowest possible fossil percentage, expressed as a fraction of the generator’s peak capacity. If the engine’s capacity is restricted to 15kW at 20% diesel, the 15kW derating ratio is divided by 20kW, or 75%.

What does DPF full engine derated mean?

A derate indicates that the computer software of an engine restricts either the vehicle speed or engine power. A derate is intended to safeguard you from inflicting harm to the engine or DPF. A variety of systems or sensors can trigger a derated state.

What does it mean when it says engine derate?

Engine derating refers to the process of reducing an engine’s power to compensate for less-than-ideal working circumstances. Derating is occasionally done deliberately to extend the engine’s lifespan and prevent significant strain or damage.

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