An engine ECU knows when to trigger DPF regeneration by using sensors, primarily a differential pressure sensor, to measure soot buildup; when soot reaches a set limit (around 45-70%), the ECU initiates active regeneration by injecting extra fuel (post-injection) to raise exhaust temperature, burning off soot. Passive regeneration happens naturally at high speeds/temperatures, but the ECU manages active cycles when this isn't enough, often showing a dashboard light.
The ECU uses various sensors to monitor the exhaust gas temperature, pressure, and flow rate to determine when active regeneration is necessary. When the DPF is ready for regeneration, the ECU injects additional fuel into the engine to increase the temperature of the exhaust gas and initiate the cleaning process.
Several factors can trigger the diesel PCM to perform regeneration, including distance since last DPF regeneration, fuel used since last DPF regeneration, engine run time since last DPF regeneration and exhaust differential pressure across the DPF.
DPF delete is performed by first physically removing the diesel particulate filter from the vehicle (assuming that all the necessary tools and programming skills are in place). The vehicle is then connected to DPF delete kits or specific tools that are capable of reprogramming the ECU.
Passive DPF regeneration
Passive regeneration occurs when the car is running at speed on long motorway journeys which allows the exhaust temperature to increase to a higher level and cleanly burn off the excess soot in the filter.
There are two main types of DPF regeneration: passive and active, however, DPF regeneration can be performed manually using a scan tool.
You should consult the handbook for your vehicle for more specific guidance on how you should drive to initiate regeneration of the DPF and clear the warning light. Nevertheless, a general rule of thumb to follow is that you should run the engine at least 40 mph and at least 2500 rpm.
When you delete the DPF without reprogramming the ECU, you risk creating a mismatch in your engine system that will affect its entire performance.
Unfortunately, the standard method for testing particulate emissions for an MOT, the metered smoke test, is now widely felt to be completely inadequate to detect malfunctioning or deliberately removed DPFs. There has been anecdotal evidence of even a Euro 5 or Euro 6 car, which has had its DPF removed, easily passing.
If your car has an automatic gearbox, change gears in manual mode, increasing the number of revolutions. However, there's no need to go as far as the rev limiter, as that won't do any good. Drive in this mode for at least 30 minutes. This will trigger a regeneration cycle and your DPF will be cleaned.
During enhanced passive regeneration, the engine ECU closes the air throttle and changes injection timing to increase the exhaust gas temperature to a level that promotes passive regeneration.
Connect the scanner to your vehicle's OBD2 port, turn on the ignition, and use the scanner's interface to initiate the regeneration process. Follow the instructions on the scanner, and make sure to keep the engine running for the duration of the process.
If you regularly drive at over 40mph for 30-50 minutes, the DPF will stay clear anyway. If you don't do this, active regeneration should occur every 300 miles or so depending on how you use the car.
Top 10 vehicles with DPF issues:
Most dpf systems will regenerate only if you do a steady 2000 to 2500 revs for at least 15 minutes.
It's illegal to delete or tamper with any part of emissions system Ad Blue, DPF , EGR etc, mot test's are getting stricter, if your vehicle shows these kind of faults on the MOT history it will make it harder to sell, any half descent mechanic/ technician/ MOT tester can find if its been tampered with.
Maintaining a clean DPF can extend engine life by reducing needless pressure on engine components. Regular cleaning reduces wear and tear, resulting in a longer engine lifespan and lower maintenance expenses.
Car Remapping and UK MOT Emission Rules
A quality remap optimises the engine's combustion process which can sometimes lead to cleaner emissions. However a remap must not involve the removal of essential emissions hardware like the DPF. Removing these components is illegal and your car will instantly fail its MOT.
Blue smoke coming from your exhaust or DPF during regeneration comes from the burning of engine oil. This means that valves or piston rings may be worn out and allowing oil into the engine, or that you're putting too much oil into the engine.
Typical Costs of ECM Replacement
Programming on ECUs depends on the make and model, but generally around $200-$600. Labour also really depends, but can be anything from $200 to $1,000. Always try and use a reliable service for ECM repairs.
If your vehicle is diagnosed as having a faulty ECU, please do not consider buying a second-hand replacement unit. In many cases it will simply not work at all, or may appear to function, but may compromise safety, performance and economy, or the correct operation of other units.
Reprogramming your ECU/ECM yourself is doable – follow this checklist to be sure you're getting the job done right: Contact your dealer to see if a replacement ECU will need programming. Get in touch with Tom's Foreign Auto Parts with your old ECU part number. Order a quality used OEM ECU – with our 6-month guarantee.
DPF filters blocking generally arise where city driving, excessive idling or light duty cycles are encountered. Or, if other engine components such as EGR valves, turbochargers, injectors are fouled or not working properly.
How does DPF regeneration occur? The regeneration occurs automatically, usually without the driver being aware that it is taking place. In the majority of cases, the process is carried out when the engine and exhaust system has reached normal operating temperature and the vehicle is travelling at over 40mph.
How Much Horsepower Can You Gain From DPF and EGR Deletes? Power Gains: Proper off-road ECU tuning after DPF/EGR removal commonly adds 30–50 HP and major torque improvements, especially under load.