A DPF is typically considered clogged when the DPF differential pressure exceeds approximately 80–100 hPa during acceleration or under load, although exact values depend on the vehicle. When the differential pressure rises too high, it indicates that the particulate filter is saturated and exhaust gas flow is restricted.
For workshops, correctly interpreting differential pressure values is one of the fastest and most reliable ways to diagnose a clogged particulate filter.
What is the DPF differential pressure sensor?
The DPF differential pressure sensor is a component of the exhaust system that measures the pressure difference between the inlet and outlet of the particulate filter.
This information is sent to the engine control unit (ECU) to monitor the filter’s condition and determine when regeneration should occur.
A DPF monitor
The sensor acts as a permanent monitoring system for the particulate filter.
Its function is to detect:
- Soot buildup in the filter.
- Restriction of exhaust gas flow.
- The right time to start regeneration.
Without this measurement, the system would not be able to determine when the filter needs to be cleaned through regeneration.
Its role in the engine
The DPF differential pressure sensor is key to the proper functioning of the emission control system.
Thanks to it, the control unit can:
- Detect DPF saturation.
- Initiate automatic regenerations.
- Prevent damage to the exhaust system.
- Keep emissions within legal limits.
When this sensor fails, the system loses track of the filter’s actual status.
Location in the vehicle
The DPF differential pressure sensor is usually located near the exhaust system and connected to the particulate filter via two small pressure tubes.
One measures the pressure before the filter and the other after. This difference allows the level of DPF clogging to be calculated.
How does the differential pressure sensor affect the diesel particulate filter (DPF)?
The sensor is responsible for informing the engine management system of the filter’s saturation level.
If the data it sends is correct, the control unit can:
- Initiate regenerations at the right time.
- Prevent excessive saturation.
- Protect the exhaust system.
But if the sensor fails or sends incorrect data, problems such as the following may occur:
- Unnecessary regenerations.
- Filter clogging.
- Activation of emergency mode.
Differential pressure values: When is the DPF clogged?
Differential pressure values increase as the filter accumulates particles. Although they vary by vehicle, there are guideline ranges used in diagnostics.
| DPF status | Approximate differential pressure |
| Clean DPF | 5 – 15 hPa |
| Moderate saturation | 20–40 hPa |
| High saturation | 40–80 hPa |
| DPF clogged | > 80 – 100 hPa |
When values exceed these levels, the exhaust gas flow is restricted.
At that point, the vehicle usually attempts to perform a regeneration.
Symptoms of a clogged DPF or faulty sensor
When the system detects abnormal DPF differential pressure values, several symptoms may appear.
Loss of power
One of the most common symptoms is a loss of engine power. This occurs because the exhaust has difficulty expelling gases. Backpressure increases and the engine loses performance.
Check Engine Light On
When the control module detects abnormal data, it may activate:
- Engine warning light.
- Particulate filter warning light.
- Emission control system fault messages.
These warnings usually indicate that the system needs to be diagnosed.
Frequent or incomplete regenerations
A faulty sensor can also cause improper regenerations.
For example:
- Regenerations that occur too frequently.
- Regenerations that are interrupted.
- Regenerations that never complete.
This causes the filter to continue accumulating soot.
Why does this cause errors in the exhaust system?
When the DPF differential pressure sensor does not function properly, the control unit receives incorrect information.
This can cause errors in the emissions control system.
Incorrect data sent to the control unit
If the sensor sends incorrect values:
- The ECU may believe the filter is clean when it is not.
- Or it may think the filter is clogged when it is not.
In both cases, operational problems arise.
Soot buildup
When the system fails to correctly detect filter saturation, regenerations do not occur on time.
This causes soot buildup and can result in a clogged DPF.
How to check the DPF differential pressure sensor
For workshops, there are several methods to check the sensor’s operation.
Checking the DPF differential pressure sensor with diagnostic tools
The fastest way is using diagnostic equipment.
The procedure consists of:
- Reading the differential pressure values in real time.
- Compare values at idle and under acceleration.
- Verifying whether the values are consistent.
If the values do not change with engine speed, the sensor may be faulty.
Checking the differential pressure sensor with a multimeter
It is also possible to test the sensor using electrical measurements.
- Locate the sensor.
- Measure the supply voltage.
- Check the output signal.
- Check the continuity of the pressure tubes.
If the signals do not match the manufacturer’s specifications, the sensor may be malfunctioning.
How to keep the sensor and DPF in good condition
Preventive maintenance helps prevent system failures.
Proper driving
Proper driving promotes filter regeneration.
It is recommended that you:
- Take long trips periodically.
- Maintain a constant speed for a few minutes.
- Avoid extremely short trips.
Regular inspections
During vehicle inspections, it is recommended to check:
- Sensor condition.
- Pressure hoses.
- Differential pressure values.
- Regeneration frequency.
Professional cleaning
When the filter is saturated, professional cleaning can restore its performance.
This allows:
- Reduce the differential pressure.
- Restore gas flow.
- Avoid unnecessary filter replacements.
What happens if you ignore sensor problems
Ignoring sensor or filter faults can lead to more serious breakdowns.
More costly breakdowns
A clogged DPF can cause problems such as:
- Damage to the turbocharger.
- Overheating of the exhaust system.
- Contamination of the engine oil.
- Complete replacement of the filter.
That is why it is important to diagnose these problems as soon as possible.
A key diagnostic tool for workshops
The DPF differential pressure sensor is one of the most important components for diagnosing problems with the particulate filter. Correctly interpreting its readings allows for the detection of blockages before more serious failures occur.
At Oxyhtech, we help workshops implement professional solutions for cleaning and maintaining particulate filters using equipment specifically designed for these types of procedures.
Do you want to offer a professional DPF cleaning service at your shop? Contact us and discover how to improve the profitability and diagnostic capabilities of your service.
Frequently Asked Questions
A clogged DPF can cause problems such as:
> Damage to the turbocharger.
> Overheating of the exhaust system.
> Contamination of the engine oil.
> Complete filter replacement.
That is why it is important to diagnose these problems as soon as possible.
Under normal conditions, a clean DPF typically registers values between5 and 15 hPa at idle. These values increase slightly when accelerating.
DPF differential pressure can be read using:
> OBD diagnostic equipment.
> Professional scan tools.
> Real-time data from the engine management system.
These values allow you to assess the filter’s condition.
