What is a DPF?
A Diesel Particulate Filter (DPF or FAP for short) is a filter found in the downpipe section of the exhaust and is specifically designed to reduce the amount of Diesel Particulate Matter (Soot/Ash) passing through. The objective of this filter is to create cleaner / more eco friendly exhaust gases being released into the atmosphere.
A diesel particulate filter will gradually become restricted and more clogged up as a normal part of it’s service life. A process called regeneration is designed to occasionally ‘clear out’ the particulate filter. Unfortunately this needs specific driving conditions and when these are not met, the degree to which the filter is blocked can surpass the engine managements ability to regenerate the filter – leading to problems with power loss (see detailed list below) and even in the absolute worst case, risk to the car due to overheating of the filter.
A blocked DPF can cause many problems including loss of power, economy and throttle response. With more extreme cases, filters that are extremely blocked can cause the engine not to start at all.
Generally speaking a blocked DPF is usually caused by another underlying issue. It is worth undertaking further diagnostics to find the route cause of the blockage.
Things what could lead to a blocked DPF:
- Short Journeys – Vehicles doing a a lot of ‘town driving’ are a more likely to block up due to the DPF not getting up to temperature. For the DPF regeneration process to work effectively and burn off the carbon deposits the engine needs to frequently get up to temperature.
- Faulty / Failed Sensors – DPF’s have several sensors that are installed before and after the filter. These sensors are fitted to monitor the Pre and Post temperature and pressure of the filter. If one or more of these sensors fail, the regeneration process may not be carried out effectively.
- Faulty / Failed EGR Valve – The EGR Valve is designed to recirculate exhaust gases back into the engine before they pass through the DPF. If the EGR is not working effectively or blocked the amount of exhaust gases passing through the DPF will be increased potentially speeding up the DPF blocking.
- Faulty / Failed Swirl Flaps – Similar to the EGR Valve the swirl flaps are fitted to help with the emissions control on the vehicle. If theses are not working effectively it can potentially speed up the DPF blocking.
- Failed Regeneration – For the DPF to regenerate there are certain conditions to be met. If these prerequisites are not met the DPF will fail to regenerate. See here for more info
Symptoms and Fault Codes
There are multiple faults codes and symptoms that can point towards a faulty / blocked DPF.
- Loss of power
- Higher fuel consumption
- Reduced throttle response
- Harder / Failure to Start
- Limp Mode
- DPF Light (yellow symbol in the top photo)
- Coil and Engine Management lights
- P2002 Particulate Trap Bank 1 Efficiency Below Threshold – P2002 00 – Malfunction (18434/P2002/008194)
- P2453 Diesel Particle Filter; Differential Pressure Sensor – P2453 00 – Implausible Signal (18885/P2453/009299)
- P2452 Diesel Particle Filter; Differential Pressure Sensor – P2452 00 – Elect. Malfunction (18884/P2452/009298)
- P2454 Diesel Particle Filter; Differential Pressure Sensor – P2454 00 – Short to GND
- P0472 Diesel Particle Filter; Differential Pressure Sensor – Signal too low – Defective
- P2458 Diesel Particulate Filter P2458 00 – Regeneration Duration
Other Related Faults
- P1958 Exhaust Gas Temperature Sensor 2 Bank 1 (G448) – P1958 00 – Short to Plus
- P2080 Exhaust Gas Temperature Sensor 1 Bank 1 (G235) – P2080 00 – Implausible Signal
- P242A Exhaust Gas Temperature Sensor 3 Bank 1 – P242A 00 – Malfunction
- P242B Exhaust Gas Temperature Sensor 3 Bank 1 – P242B 00 – Range/Performance
- P246E Exhaust Gas Temperature Sensor 4 Bank 1 – P246E 00 – Electrical Malfunction
- P246F Exhaust Gas Temperature Sensor 4 Bank 1 – P246F 00 – Implausible Signal
DPF Removal Options
Stainless DPF Downpipes
we offer a range of DPF Delete options for most TDi engines. For certain makes and models we can offer a complete Stainless Steel Downpipe which completely removes the DPF section of the exhaust and fits directly in place of the standard downpipe. For the models we don’t have off the shelf downpipes for, we have all the facilities in our workshop to custom make them on the car.
Standard DPF Filter Removal
Another option we have is to cut out the filter from the DPF housing itself, still removing the problem but visually leaving the DPF Housing in its original place for visual inspections. This method can also be carried out at home if you have the correct tools and equipment available.
When deleting the DPF in the software we remove all of sensors other than the Pre-Turbo EGT Sensor and Lambda Sensor.
Other companies tend to keep all of the sensors in place and although the some of these sensors are not in use they can cause issues further down the line. If any of these sensors fail it can cause the car to go into limp mode or turn on the fans constantly.
EGR Removal After DPF Delete
After deleting the DPF you are also able to delete the EGR Valve, this valve is used to lower the emissions of the car but are often prone for failing. The valve works by recirculating some of the exhaust gases back into the engine through the air intake system, reducing the amount of emissions that exit the car.
The problem lies with the exhaust fumes that contain carbon deposits, these fumes are constantly being recirculated through the engine which over time will cause a build-up of the carbon deposits in the intake manifold and other in other parts including the EGR valve. This build up in the valve is often what causes them to fail.