What are the risks of driving with a clogged particulate filter?

Driving with a clogged particulate filter can cause a loss of power, increased fuel consumption, turbo overload, and serious engine damage. If the DPF reaches a high level of saturation, the vehicle may enter emergency mode and require professional cleaning or even replacement of the filter.

For repair shops, quickly identifying a clogged DPF and applying the appropriate solution is key to preventing major breakdowns and providing effective service to the customer.

What is a diesel particulate filter?

The diesel particulate filter (DPF or FAP) is a component of the exhaust system responsible for trapping solid particles generated during diesel engine combustion.

Its main function is to reduce pollutant emissions to comply with environmental regulations.

How a diesel particulate filter works

The DPF acts as a high-temperature ceramic filter that:

• Traps the soot produced by combustion.
• Stores the particles inside.
• Periodically removes them through a process called regeneration.

If this process does not occur correctly, the filter begins to become saturated until it becomes clogged.

Types of Particulate Filters

There are several types of particulate filters depending on the regeneration system used.

Passive regeneration filters

They operate using the natural temperature of the exhaust.

• They regenerate when the vehicle is driven at high speeds.
• They are common in highway driving.
  

Active regeneration filters

The vehicle’s system injects additional fuel to raise the exhaust temperature and burn off accumulated particles.

These are the most common in modern vehicles.

Filters with additives

Some systems use specific additives that facilitate the combustion of soot at lower temperatures.

This system is common in PSA Group vehicles.

How can you tell if the particulate filter is clogged?

A clogged particulate filter usually shows clear symptoms such as a loss of power, increased fuel consumption, or the DPF warning light coming on in the instrument cluster.

Mechanics can detect a clog by:

• Reading the DPF differential pressure.
• OBD diagnostics.
• Measuring exhaust backpressure.
• Analyzing failed regenerations.

When the differential pressure exceeds certain values, the filter is saturated.

Symptoms of a clogged particulate filter

• Loss of power.
• Increased fuel consumption.
• Activation of emergency mode.
• Dark smoke from the exhaust.
• Frequent regenerations.
• DPF warning light on.

The sooner the problem is detected, the easier it will be to fix.

Drop in engine RPM

One of the lesser-known symptoms of a clogged particulate filter is an irregular drop in engine RPM.

This occurs because:

• Exhaust backpressure increases.
• The engine has greater difficulty expelling exhaust gases.
• The performance of the combustion system is affected.

In some cases, the vehicle automatically limits RPM to protect the engine.

What does the particulate filter warning light indicate when it comes on?

The DPF warning light is a clear indication that the filter needs attention.

Depending on the vehicle, it may indicate:

• Moderate saturation level: The car requires regeneration by driving at higher RPMs.
• High saturation: It is recommended to visit a service center for forced regeneration or professional cleaning.
• Critical saturation: The vehicle may enter emergency mode, limiting power to prevent damage.

Risk of particulate filter clogging

DPF clogging occurs when the accumulation of particles exceeds the system’s regeneration capacity.

This is mainly caused by:

• Frequent city driving.
• Short trips.
• Problems with the EGR, injectors, or turbo.
• Use of the wrong oil.
• Interrupted regenerations.

When the filter becomes completely clogged, regeneration is no longer effective.

Consequences of driving with a clogged particulate filter

• Damage to the turbocharger due to excessive backpressure.
• Overheating of the exhaust system.
• Contamination of the engine oil.
• Increased fuel consumption.
• Severe loss of power.
• Possible internal engine damage.

In extreme cases, the vehicle may become completely immobilized.

Common problems caused by clogging

• EGR valve malfunctions.
• Problems with the differential pressure sensor.
• Injectors with poor atomization.
• Damaged turbocharger.
• Faulty temperature sensors.

That is why it is important to always perform a complete system diagnosis.

Particulate filter regeneration

Regeneration is the process by which the DPF removes accumulated particles.

• Passive regeneration: This occurs when driving at a constant speed for a certain period of time.
• Active regeneration: The vehicle’s system increases the exhaust temperature to burn off the soot.
• Forced regeneration: Performed at a service center using diagnostic equipment.

How to tell if your car is regenerating its filter

Several signs may appear during regeneration:

• Temporary increase in fuel consumption.
• Higher idle speed.
• Engine fan running.
• Strong odor from the exhaust.

Many drivers are unaware that their car is regenerating.

What to do if your filter is regenerating

It is best not to interrupt the process.

• Keep the vehicle running.
• Drive at a constant speed.
• Avoid turning off the engine during regeneration.

Repeatedly interrupting the process can cause the filter to become clogged.

Regeneration failures

Regeneration may fail for various reasons.

• Faulty pressure sensor.
• EGR problems.
• Worn injectors.
• Use of incorrect oil.
• Excessive filter saturation.

When the filter is too saturated, the system can no longer regenerate it.

What happens if the filter cannot be regenerated?

If the DPF reaches a critical saturation level, regeneration is no longer feasible.

In that case, there are two options:

• Professional cleaning: This removes accumulated ash and soot without replacing the filter.
• Filter replacement: This is only recommended when the filter is structurally damaged.

For many repair shops, professional cleaning is the most cost-effective solution.

Particulate Filter Maintenance

Proper maintenance reduces the risk of clogging.

• Take long drives periodically.
• Use approved low-SAPS oil.
• Check the EGR and injectors.
• Diagnose failed regenerations.
• Perform preventive cleanings.

Cleaning methods

• Forced regeneration.
• Chemical cleaning.
• Cleaning with specialized machines.
• Ultrasonic cleaning. 

However, the only effective filter cleaning is that performed using a specialized professional machine, such as Oxyhtech’s DPFs, which guarantee up to 100% effective cleaning, while other methods do not exceed 70%.

Professional DPF cleaning machines allow you to restore the filter’s flow without having to replace it.

An increasingly in-demand service at repair shops

Problems related to the particulate filter are becoming increasingly common in modern diesel engines. Knowing how to correctly diagnose a clogged DPF and apply the appropriate solution helps prevent serious breakdowns and offers high-value service to the customer.

At Oxyhtech, we help workshops implement professional solutions for cleaning and maintaining particulate filters with equipment specifically designed for this task.

Would you like to introduce or improve your workshop’s DPF cleaning service? Contact us and we’ll help you choose the best solution for your business.

Frequently Asked Questions About Particulate Filters