Peugeot and Citroën DPF additive fault: warnings, codes and what to do

What the warnings mean

PSA diesels with the additive filter give drivers a set of messages. They are not all the same fault.

• "Particle filter additive level too low"

  The ECU thinks the additive is nearly gone, based on its counter. It may be right, or the counter may be wrong, or the pump may not be dosing. A refill and counter reset fixes the first case only.

• "Risk of particle filter blocking"

  The filter is loading with soot. The car may ask you to drive at speed. If the additive system is faulty, this will not work reliably.

• "Anti-pollution system faulty" or engine fault

  A general warning. The cause can be an additive pump code, a pressure sensor code or a soot loading code. A scan tells us which.

• Power reduced

  The ECU is limiting output to protect the engine. At this stage the filter is heavily loaded, and a forced regeneration may be needed.

The codes behind the messages

Exact wording varies by ECU and tool. These are the usual meanings on PSA diesels.

• P15B3: additive level or quantity below minimum

  On many PSA ECUs this means the calculated additive quantity has dropped below the minimum. It is a level fault, not necessarily a pump fault.

• P1435: multiplexed additive pump

  A CAN network fault or a pump fault. The ECU cannot communicate with the pump properly. Wiring is the more likely cause than the pump.

• P1434: pump supply or control circuit

  An electrical fault in the circuit serving the pump. A fuse, earth or connector is likelier than a failed pump.

• P2463: DPF soot accumulation

  Soot has built up beyond the expected limit. It is often a consequence of missing additive, but it also appears when the filter is simply old or the driving is too gentle.

• P2002: DPF efficiency below threshold

  The filter is not trapping soot as well as the ECU expects. It can be damage, heavy loading, or a sensor issue. We test before assuming the filter is dead.

• U0118: lost communication with the additive module

  A network code showing that contact with the additive control module has been lost. It often appears alongside P1435.

What happens to the filter when dosing stops

The Eolys additive lets soot burn at around 450°C instead of about 600°C. When dosing stops, the additive already in the soot gets used up over time. Regenerations then need more heat than short journeys provide, so they stall or never begin. Each failed attempt wastes fuel and leaves more soot behind.

The path is predictable. First the codes and the additive message appear. Next, the soot load rises and the dash warns of a risk of blocking. Then differential pressure climbs, the ECU limits power, and the filter reaches a point where normal driving cannot clear it. Oil can also be diluted by the extra fuel injected during failed regenerations, which is worth watching on cars that have had a long run of them.

How long this takes depends on how the car is used. A van on motorway runs may take months. A school-run car doing short hops may take weeks. That is why we recommend diagnosing as soon as the first warning shows.

When a regeneration is needed

Fixing the additive system stops the problem getting worse. It does not always remove the soot already in the filter.

• Soot load low to moderate

  After the repair, normal driving or a sustained run at speed is often enough to clear it. We check the soot mass in live data and tell you.

• Soot load high

  A service regeneration, run with the diagnostic tool, burns the soot off under controlled conditions. We run this on site where it is safe to do so.

• Filter heavily blocked

  Where soot loading and pressure readings are beyond safe limits, a normal regeneration may not be possible. We tell you plainly and talk through the options.

• What we will not do

  We do not remove the filter or fit software that switches off emissions systems. That is not a repair, and it is not legal for road use.

DPF additive or AdBlue: which warning is yours?

Drivers often blame the wrong fluid. The DPF additive warning belongs to the Eolys system, which feeds the particulate filter. AdBlue warnings belong to the SCR system, which treats NOx. They have different tanks and filler points, and filling one does nothing for the other.

On Euro 6 Peugeots and Citroëns from around 2014, both can be fitted. If your dash shows an AdBlue countdown as well as a filter message, there are two faults to deal with. We check the VIN, read both systems and price each repair separately.

How we sort a DPF additive fault

The aim is to find out whether you have a level fault, a pump fault, a wiring fault or a filter fault, before anything is bought.

• Scan all modules and note the order

  We read codes from the engine ECU and the network modules, with freeze-frame data, to see which fault came first.

• Check additive live data

  Additive quantity, refuel detection and pump status show whether the system is dosing and whether the counter is believable.

• Read soot mass and pressure

  Soot load and the pressure difference across the filter tell us how far the filter has loaded and whether a regeneration is needed.

• Test the pump circuit

  Supply, earth and CAN lines are measured at the pump connector, and the pump is commanded on from the tool.

• Look at the pouch, housing and lines

  A visual check under the car for damage, leaks, split pouches and corroded plugs.

Repair path for a DPF additive fault

We diagnose first and give you a fixed price before any work starts. No fix, no fee on the agreed outcome.

We come to you: drive, yard, depot or roadside, 6am to 9pm, seven days a week including bank holidays. Many additive faults are put right in a single visit. Where parts are needed, we confirm them against your VIN, agree the price and return to fit them.

• Refill and counter reset

  For a genuine low level, the correct Eolys fluid is added and the ECU counter is reset with diagnostic equipment.

• Wiring, connector or pump repair

  Where the pump circuit is at fault, we repair or replace the faulty part and code it.

• Service regeneration

  If soot is high, we run a controlled regeneration with the diagnostic tool and check the readings afterwards.

• Road test and recheck

  A test drive, a rescan and a final live-data check make sure the warnings have gone for good.

• Mobile diagnosis and simple fix: From £249 Callout, full diagnosis and fixes such as a counter reset or connector repair.
• Additive pump, pouch or tank: Fixed price after diagnosis Parts matched to your VIN and agreed before work starts.
• Service regeneration: Quoted on the day Depends on how much soot is in the filter.

P15B3 questions

Is particle filter additive level too low the same as P1435?

No. A low-level message is usually an additive quantity code such as P15B3. P1435 is a pump or network fault. They can appear together, so we test the whole system.

How many miles can I drive with risk of particle filter blocking?

We cannot give a safe figure. It depends on the soot load and how you drive. Treat the message as urgent, and have it diagnosed before the car goes into limp mode.

Can I fix the warning by driving at motorway speed?

Sometimes, if the additive system is working and the filter only needs a burn. If dosing has failed, a long drive may not clear the message, and it can return within days.

What do P2463 and P2002 mean on a PSA diesel?

P2463 means soot has accumulated beyond the expected level. P2002 means the filter efficiency is below the threshold. Missing additive can lead to the first, but the filter and sensors need testing as well.

Will you take the filter off if it is blocked?

No. We do not remove filters or fit software that disables emissions equipment. We look at regeneration, repair and, where needed, a proper replacement route.

How do I know if my car even has the additive system?

Look for a second small filler or tank near the fuel tank, or ask us. We check the VIN and tell you whether your car has Eolys, AdBlue or both.