Peugeot and Citroën additive tank faults: P1434, P1435 and P15B3 diagnosed and fixed

What the additive warning looks like

Peugeot and Citroën usually show the engine or particulate filter warning with a message such as "Risk of particle filter blocking" or "Particle filter additive level too low". Some cars go into reduced power. The message does not name the code; a diagnostic read is needed to see P1434, P1435 or P15B3.

The additive is dosed into the fuel tank each time you fill up. It lowers the temperature at which soot in the particulate filter burns off. Without it, regenerations fail, the filter blocks faster and the car can end up in limp mode. That is why these codes need dealing with rather than clearing and ignoring.

This system is not AdBlue. AdBlue is injected into the exhaust to reduce NOx. The additive is mixed into the diesel to help the particulate filter clean itself. Some Peugeot and Citroën models have both, and the two are often confused.

What P1434, P1435 and P15B3 usually mean

Exact code definitions vary between engine ECUs and diagnostic tools, so we always read the full manufacturer description. These are the meanings and causes we see most often.

• P15B3: calculated additive level below minimum

  The ECU keeps a running count of how much additive has been used since the tank was last filled. When the count reaches the minimum, P15B3 sets. Often the tank really is empty. Sometimes it has been refilled but the counter was never reset, so the ECU still thinks it is empty.

• P1434: additive pump or circuit fault

  Usually reported as a fault in the additive pump control circuit. Common causes are a failed pump, a corroded connector near the fuel tank, or a damaged wire. The pump sits under the car and gets road salt and water, so connectors are a regular culprit.

• P1435: additive pump communication fault

  On later systems the additive pump talks to the engine ECU over the vehicle network. P1435 usually means that conversation has been lost or the pump has reported an internal fault. Power, earth and the network wiring are checked before the pump itself is condemned.

• Wrong additive type

  Earlier systems and later pouch-type tanks use different additive fluids. Filling with the wrong one, or a non-approved fluid, can cause dosing faults and damage. We confirm the correct fluid for the car by VIN before refilling.

• Split or leaking additive pouch

  Later Peugeot and Citroën systems hold the additive in a flexible pouch inside a rigid housing. A split pouch or leaking line loses fluid, which leads to P15B3 far sooner than expected. We inspect the tank and lines before refilling so the new fluid is not lost.

What we check before anything is replaced

A tank or pump for this system is not cheap. We confirm the fault with manufacturer-level diagnostics first.

• Confirm the car actually has an additive system

  Not every Peugeot or Citroën diesel uses one. The 1.6 and 2.0 HDi engines commonly do. The 1.5 BlueHDi generally does not. We check the equipment by VIN so you do not buy parts for a system the car does not have.

• Full code read with manufacturer descriptions

  We read the engine ECU and any additive module, including the exact fault text and whether each code is current or historic.

• Additive level and refill history

  We check the real fluid level against the ECU's calculated level. If they do not match, the counter needs resetting rather than a new tank.

• Pump operation, power, earth and network

  The pump is commanded on and its response checked. We test the supply, earth and communication wiring at the connector under load before the pump is blamed.

• Particulate filter condition

  Low additive can leave the filter heavily loaded. We read soot loading and back-pressure so we know whether a regeneration is needed after the additive fault is fixed.

Repair options and pricing

Fixed price before work starts. No fix, no fee on the agreed outcome. Written warranty.

Many additive faults are fixed in one visit: a refill with the correct fluid and a counter reset, or a connector and wiring repair. If the pump or tank assembly has failed, we confirm it on the first visit, quote a fixed price, and return to fit the part and code it to the car.

• Refill and additive counter reset

  The tank is refilled with the correct approved fluid for the car and the ECU counter is reset with diagnostic equipment. Without the reset, the warning returns.

• Wiring and connector repair

  Corroded or damaged connectors and wiring near the tank are repaired and protected, then the pump is retested.

• Pump or tank assembly replacement

  Where the pump has failed or the pouch has split, the part is replaced, primed and coded so the ECU recognises it.

• Assisted regeneration if needed

  If the filter has loaded up while the additive was low, we run a regeneration once dosing is working again.

• Diagnosis and straightforward fix: From £249 Covers callout, diagnosis and fixes such as a refill and reset, or a wiring or connector repair.
• Additive pump replacement: Fixed price after diagnosis Only once power, earth and communication have been proven good.
• Additive tank or pouch assembly: Fixed price after diagnosis Quoted before any part is ordered.

Software — coding and resets only

The software work on this system is limited to resetting the additive counter and coding a new pump or tank to the car. We repair the additive system so the particulate filter keeps working as designed.

Which Peugeot and Citroën models get these codes

We see P1434, P1435 and P15B3 mostly on Peugeot and Citroën diesels with the 1.6 HDi and BlueHDi and the 2.0 HDi engines. That includes models such as the Peugeot 308, 3008, 5008 and Partner, and the Citroën C4, C4 Picasso, Berlingo and DS models of the same era.

The current 2019–2026 Berlingo, Partner and Vauxhall Combo with the 1.5 BlueHDi generally do not use an additive tank. If your van shows AdBlue codes such as P20EE, see our Berlingo, Partner and Combo page instead.

Why clearing the code is not enough

Clearing P15B3 without refilling and resetting the counter just brings it back. Clearing P1434 or P1435 without fixing the wiring or pump means the filter keeps loading with soot. Left long enough, that turns an additive repair into a much more expensive particulate filter problem.

Frequently asked questions

What does P1435 mean on a Peugeot?

P1435 is usually reported as an additive pump communication or control fault on the particulate filter additive system. Causes include a failed pump, a corroded connector or a wiring fault. The exact description depends on the ECU, so we read it with manufacturer-level equipment before replacing anything.

What does P15B3 mean on a Citroën?

P15B3 usually means the calculated additive level is below the minimum. The tank may be empty, or it may have been refilled without the counter being reset. Either way, the correct fluid and a proper reset are needed.

Is the additive tank the same as AdBlue?

No. AdBlue is injected into the exhaust to reduce NOx. The additive (often called Eolys) is dosed into the fuel to help the particulate filter burn off soot. They are separate tanks with separate fault codes.

Can I just top up the additive myself?

The ECU needs its additive counter reset after a refill, which needs diagnostic equipment. The correct fluid type also depends on the system. We refill with the right approved fluid and reset the counter in the same visit.

Do I need a new additive tank for P1434?

Not necessarily. P1434 often comes from a connector or wiring fault near the tank. We test the pump circuit first and only quote a pump or tank once the wiring has been proven good.

What happens if I ignore an additive fault?

Without additive, the particulate filter cannot regenerate properly. It blocks faster, the car may go into limp mode, and a relatively simple repair can turn into a filter replacement.