6.7 Cummins Manual Regen Switch – What’s this and How to Use?

The 6.7 Cummins is a straight-six turbodiesel engine introduced in 2007. It is the latest release of the B series engines. The 24-valve turbodiesel was launched to replace the 5.9L due to the introduction of tightened emission laws.

Key features and my opinion about the engine

• Production years:2007-now
• Average lifespan of 6.7 Cummins:350,000-500,000 miles
• Fuel supply type:Common Rail
• Power range:150-420 hp
• Fuel efficiency:bad
• Engine block material:cast iron
• Engine reliability score:high
• The most common problems:fuel supply issues, head gasket failure, turbocharger problems.

What is a 6.7 Cummins DPF System?

When diesel fuel combusts, it emits microscopic particles into the exhaust gas. These solid particles are called diesel particulates and contain many chemical components that are dangerous to human health.

Although the 6.7 Cummins is equipped with oxidation catalysts called DOCs designed to clean exhaust gas before it is emitted to the environment, they don't capture these solid particulates when cleaning - and this is where the Diesel Particulate Filter system comes in.

The DPF filters are designed to capture these particulates, also called diesel soot, and keep them from being emitted into the environment. Built from ceramic materials, the DPF is designed like an ordinary catalytic converter and uses the same honeycomb structure.

To ensure that the DPF system doesn't clog and cause performance problems, the 6.7 Cummins burns the collected soot into harmless ash through regeneration.

The DPF regenerates in two automatic cycles; passive and active. Passive regeneration occurs when the exhaust gas temperatures reach or exceed 950 degrees Fahrenheit. But since these temperatures aren't always reached, active regeneration is initiated to clear the DPF and keep it from clogging. During this active regeneration cycle, diesel is injected into the exhaust system. The fuel then heats the exhaust gas through the oxidation catalysts and burns the DPF particulates. Both the passive and active regen cycles happen automatically.

Besides the passive and active regeneration cycles, there is another process called forced or manual regeneration.

Forced Regeneration, Manual Regen Switch and How to Use It

Mostly referred to as regen, regeneration of the diesel particulate filter is the process of burning soot accumulation from the 6.7 Cummins DPF system. This process happens in three cycles called passive, active, and forced regen.

While the first two happen automatically as your diesel truck goes down the road, forced regeneration has to be initiated manually by the driver. The 6.7 Cummins has a manual regeneration switch or button to force the DPF into the regeneration process.

Before looking at what this button is, and how you can use it, let's first understand what forced regeneration is.

In the 6.7 Cummins diesel engine, forced regeneration overrides the soot accumulation levels calculated by the electronic control unit. Sometimes the soot accumulation can be too high for passive or active regeneration. At this point, your vehicle might be unable to move, which is when you have to initiate the forced regeneration process. Manual regen is the highest level of regeneration.

The Manual Regen Switch/ Button

As mentioned earlier, the exhaust gas temperatures have to be 950 degrees Fahrenheit or higher for the regeneration process to initiate automatically. The manual regeneration button is built to initiate this process manually. The manual regen switch is used to clear soot from the DPF while the vehicle is stationary. It is more like the dealer regeneration minus the fancy equipment.

How and When Do You Use the Manual Regen Switch/ Button

You should use the manual regen switch when the DPF (Diesel Particulate Filter) light illuminates or begins to flash. This warning indicates that soot in the DPF filters has accumulated to the required limit. The light means your 6.7 Cummins DPF system is blocked and requires immediate action.

The following is a step-by-step guide on performing a regeneration using the manual regen switch on your 6.7 Cummins.

• Find an appropriate parking space, and engage the parking brakes. Place the transmission pedal in NEUTRAL or PARK. The manual regeneration should take between 45 and 60 minutes to complete.
• While picking the ideal parking space, ensure no obstacles around the exhaust area.
• Switch off your fast-idle and power take-off buttons before pressing the manual regen switch.
• At this point, it is safe to push the manual regeneration switch. During the process, you will notice an increase in engine speed. You will also hear a different sound coming from the turbocharger. Once the diesel particulate filter system is regenerated, your 6.7 Cummins will return to average idle speed.
• Pay extra attention during the regen process. If you notice unsafe conditions, kill the engine immediately, and depress the brake or throttle pedals to exit the manual regen process.
• The exhaust gas temperatures will remain high for three to five minutes after the process.

You can always reference your 6.7 Cummins manual for more precise instructions.

How to Tell if the 6.7 Cummins Manual Regen Was Successful

The first rule of thumb is the time required for a successful manual DPF regeneration - at least 45 minutes and one hour at most. This is the time the system requires to build up the right temperature around the exhaust gas and all other components and inject diesel fuel into the exhaust streams. During this time, the reaction of fuel and the exhaust gas in the oxidation catalysts will also take place and burn the accumulated soot into harmless ash. There may be slight variances, but these happen between 45 and 60 minutes.

If the regen process completes within this timeframe, you can be confident of hitting the road knowing that your DPF filters were cleared successfully.

Another indicator of a successful regen is the unique smell from the exhaust tailpipe during the process.

The constant temperature increase around the exhaust components during the process indicates a successful regeneration. You can monitor the temperature changes as the process moves from beginning to end with an infrared thermometer.

• What If the Manual Regen Process Lasts More Than 60 Minutes?

Maybe so far, you are remembering your previous regen and realizing that it lasted more than one hour. While this is not normal, it doesn't necessarily mean that your 6.7 Cummins did not regenerate successfully.

Sometimes your manual regeneration lasts longer than an hour. This indicates that the exhaust gas temperatures aren't rising fast enough. If it takes longer before the required temperatures are attained, the regen process will also take longer to complete.

There are other factors that can slow down the regeneration process in your 6.7 Cummins, but slow temperature build-up is the main reason.

• What If The Manual Regen Process Finishes Before 45 Minutes?

While it's okay for a regen process to last a little longer than an hour, it should concern you if it drops out within the first 30 minutes. It means that your ECU detected a problem that forced it to end the regen process. If the computer system detects a fault with one or more critical parts of the regen process, it has to bring it to an instant halt.

The system will also send in a trouble code associated with the error to paint a clearer picture of what caused the stop. You should fix the fault and restart the regen process.

Is It Okay To Change The Engine Oil After The Manual Regen?

If you take your 6.7 Cummins to a dealer for a DPF regeneration, they usually change the engine oil once the DPF filters have been cleaned. Like the dealer regen, you should change your oil after performing a manual regeneration to your 6.7 Cummins.

The engine is usually subjected to extremely high temperatures during the regen process. You should consider changing your oil with high-quality, fresh oil - one with low quantities of Sulphated Ash.

In Conclusion

Diesel particulate filter clogging is one of the most notorious problems with the 6.7 Cummins. It's awful for a turbodiesel engine to run with a clogged DPF. When the particulate filter clogs, it causes the 6.7 Cummins to build up backpressure, making the engine strain.

To limit the negative effects of this problem, the 6.7 Cummins is built with the ability to burn the DPF-clogging soot automatically in a process called DPF regeneration. And if the automatic regen doesn't happen, the turbodiesel can use a manual regen switch to force the system to clear the clogging soot.

This manual regen button is handy, especially when the clogging soot is too much for the automatic regen. It is also handy for drivers living in areas that do not allow vehicles to generate the much-needed heat to burn off the soot automatically.