P1437 on 2004-2011 Peugeot 407 2.0 HDi: DPF Additive System Fault Causes and Fixes

What's Unique About the 2004-2011 Peugeot 407

Unlike many diesel vehicles that rely solely on high exhaust temperatures for DPF regeneration, Peugeot/Citroën (PSA) vehicles use this active Eolys additive system. This design makes regeneration more effective at lower temperatures but adds complexity and unique failure points. The entire system—comprising a special fluid pouch or tank, a dosing pump, an injector, and a dedicated ECU or BSI function—is a common source of the 'Depollution System Faulty' message on the dashboard as these vehicles age. The system's reliance on software counters rather than a physical level sensor is a key characteristic; failure to reset these counters with a tool like Diagbox after a refill will cause persistent faults.

Symptoms You May Notice

• "Depollution system faulty" or "Engine fault: Repair needed" message on the instrument cluster.
• "Risk of particle filter clogging" warning message.
• Vehicle may enter limp mode (reduced power and speed).
• Check engine light is illuminated.
• Potential for failed emissions tests.
• Slight increase in fuel consumption.

Most Likely Causes

1. Faulty DPF Additive Pump 🔴 High Probability The pump is an electro-mechanical part located under the vehicle, exposed to the elements. The internal motor or electronics can fail over time, or the pump can be damaged by running dry if the Eolys fluid is not refilled in time.
   How to confirm: Use a diagnostic tool like Peugeot Planet/Diagbox to run an actuator test on the pump. If the pump doesn't respond or makes no noise, it has likely failed. This is often accompanied by codes P1434/P1435.
   Typical fix: Replace the entire additive pump and tank/pouch assembly. The system must then be bled and the ECU counter reset using a diagnostic tool.
   Est. part cost: $150-$300
2. Damaged Wiring or Corroded Connectors 🟡 Medium Probability The wiring loom to the additive pump runs underneath the car and is susceptible to water ingress, road salt, and physical damage, leading to corroded pins or broken wires. This can cause intermittent or permanent communication loss.
   How to confirm: Visually inspect the wiring harness and connector at the additive tank. Check for continuity and voltage at the pump's connector using a multimeter. A user on the French Car Forum fixed a related code (P1471) by finding wide pin gaps in a connector, causing a poor connection.
   Typical fix: Repair the broken/corroded section of the wiring harness and clean or replace the connector. Ensure the connection is sealed against moisture.
   Est. part cost: $10-$50
3. Empty Eolys Additive Fluid Pouch/Tank 🟡 Medium Probability
   How to confirm: Check the additive level using a diagnostic tool or by physically inspecting the pouch/tank. This fault is often accompanied by code P1445 (additive level low). The system calculates the level, it does not measure it directly, so a diagnostic check is most reliable. 🎬 Watch: How to refill Eolys fluid and reset the system
   Typical fix: Refill the tank or replace the pouch with the correct generation of Eolys fluid (e.g., Eolys 176, Infineum F7995). The additive level counter in the ECU must be reset afterward using Diagbox or a similar tool.
   Est. part cost: $50-$150
4. Faulty Fuel Cap Sensor ⚪ Low Probability → Shop Fuel Tank Cap The system uses magnets in the fuel cap and a sensor on the filler neck to detect when the car is refueled, which triggers the additive pump. If this sensor fails, the pump won't be commanded to dose, eventually leading to a system fault.
   How to confirm: Scan for code P2408 (Fuel Cap Sensor). With the engine off, remove and replace the fuel cap; you should hear the additive pump prime for a few seconds shortly after. If not, the sensor may be faulty. This is a well-documented cause on owner forums.
   Typical fix: Replace the fuel filler neck sensor. Ensure the magnets are present in the fuel cap.
   Est. part cost: $30-$60

Rare But Worth Checking

• Clogged Additive Injector: The small injector that introduces the fluid into the fuel tank can become blocked. This is less common than pump or wiring failure but worth checking if a new pump doesn't resolve the issue.
• Additive ECU / BSI Fault: In rare cases, the control module (either a separate additive ECU or the main Body Systems Interface/BSI) that commands the pump can fail. This should only be considered after all other causes are ruled out.

Diagnosis Steps

1. Connect a diagnostic scanner capable of reading Peugeot-specific codes (such as Peugeot Planet 2000 or Diagbox). Generic OBD-II readers may not correctly interpret this code or may miss related faults.
2. Read all fault codes from the engine ECU and the BSI (Body Systems Interface). Note any codes related to the additive system (P1434, P1435, P1445, U0118, P2408).
3. In the scan tool's live data, check the additive fluid level status and the total amount of additive injected. This will confirm if the tank is reported as empty and if the counters are plausible.
4. Locate the additive tank under the vehicle, typically next to the fuel tank, often under a plastic cover. Visually inspect the wiring harness and connector for any signs of corrosion, chafing, or physical damage.
5. Using the actuator test function in your scan tool, command the additive pump to run. Listen for an audible priming or whirring/clicking sound from the pump.
6. If the pump does not activate, use a multimeter to check for 12V power and ground at the pump's electrical connector when the test is running. This will differentiate a bad pump from a wiring issue.
7. If power and ground are present but the pump does not run, the pump has failed and needs replacement.
8. If power is not present, the fault lies in the wiring harness or the controlling ECU/BSI. Trace the wiring back towards the front of the vehicle, checking for breaks.
9. After any repair (pump replacement or fluid refill), you MUST use the scan tool to perform the 'Replacement of the additive tank' or 'Filling of the reservoir' procedure. This resets the additive level counters in the ECU. Failure to do so will cause the fault to persist even with new parts.

Parts You'll Likely Need

• DPF Additive Pump & Tank Assembly (OEM #9672419980 (Verify with VIN, several versions exist)) — This is the most common failure point for this code. The pump motor or internal electronics fail, requiring replacement of the whole unit.
  Trusted brands: PSA Genuine, VDO, Meat & Doria
  OEM price range: $250-$400
  Aftermarket price range: $150-$300
• DPF Additive Fluid (Eolys) (OEM #9736A1 (Eolys 176 / Infineum F7995)) — Needed to refill the system if the tank is empty or when replacing the pump assembly. Using the correct fluid type is critical; this generation of 407 typically uses Eolys 176 or Infineum F7995.
  Trusted brands: Walker Eolys 176, Infineum F7995
  OEM price range: $100-$150
  Aftermarket price range: $50-$90

Related Codes That Often Appear With This One

• P1434 / P1435 — These codes are in the same family and point directly to an additive pump electrical fault (P1434) or a communication/CAN bus fault with the pump (P1435). They frequently appear together with P1437.
• P1445 — This code indicates the additive level is below the minimum threshold, meaning the tank is reported as empty.
• U0118 — A generic CAN bus code for 'Lost Communication With Fuel Additive Control Module'. It often appears with P1435, indicating a wiring or module communication problem.
• P2408 — Indicates a fault with the fuel cap sensor circuit, which is a critical input for the additive dosing logic.

Platform-Specific Known Issues

• The additive system counter MUST be reset with a diagnostic tool after refilling the fluid or replacing the pump. The car has no physical level sensor; it calculates the remaining fluid based on this programmed counter. If not reset, the car will still think the tank is empty and the fault will not clear.
• Accessing the pump requires removing a plastic undertray, which can be held on by several 10mm bolts. The pump itself is then typically held by three more 10mm bolts.

Mechanic-Grade Diagnostic Values

• Additive Pump Connector - Power Supply Pin — expected: ~12V (Battery Voltage). Failure: 0V or significantly lower voltage when the pump actuator test is running indicates a wiring or fuse issue.
• Additive Pump Connector - Ground Pin — expected: Near 0 Ohms continuity to chassis ground.. Failure: High resistance or an open circuit (OL) indicates a bad ground connection, which is a common failure point.
• Additive Pump Connector - CAN/LIN Bus Pins — expected: Approximately 2.5V on each of the two thinner communication wires, with slight fluctuations during data transfer. One line will be slightly above 2.5V and the other slightly below.. Failure: A flat line, 0V, or battery voltage on these lines points to a communication breakdown, either in the wiring or the controlling module (BSI/Additive ECU).

Hidden / Shadow Codes Worth Checking

• F017: Fault: No communication with the diesel additive pump. This is a BSI (Body Systems Interface) internal fault code that points directly to a communication line break or a faulty pump ECU. (see via This code is typically only visible in the BSI module when scanned with Peugeot/Citroën specific tools like Diagbox or PP2000.)

Scan Tool Commands That Help

• Diagbox / Peugeot Planet 2000 (PP2000): Actuator Test: Additive Pump — This is the primary test to confirm if the pump motor is functional. When activated, you should hear the pump make a whirring or clicking noise. If there is voltage at the pump but no noise, the pump has failed.
• Diagbox / Peugeot Planet 2000 (PP2000): Configuration / Replacement Parts: Filling of the reservoir / Replacement of the multiplexed additive pump. — This procedure is mandatory after refilling the Eolys fluid or replacing the pump/tank assembly. It resets the software counters in the BSI or additive ECU. Failure to perform this reset will result in the fault code persisting even with new parts.
• Diagbox / Peugeot Planet 2000 (PP2000): Parameter Measurement: Diesel Additive System — Use this to view live data such as 'Calculated Additive Level', 'Total Injected Additive Quantity', and 'Distance Since Last Regeneration'. This helps verify if the system is tracking usage correctly and confirms if the ECU thinks the tank is empty.
• Diagbox / Peugeot Planet 2000 (PP2000): BSI > Configuration > Manual Configuration > Vehicle Configuration > Type of DPF (FAP) system — For off-road use or where DPF systems have been physically removed, this setting can be changed to 'absent' to disable the additive system warnings in the BSI. This is an advanced procedure and should not be done on a road-going vehicle with an active DPF.

Wiring & Ground Locations

• Additive Pump Connector — Directly on the additive pump/tank assembly, located under the vehicle near the fuel tank, usually protected by a plastic shield.. This 4-pin connector is highly exposed to road salt and water, making it a primary point of failure due to corrosion on the power, ground, and communication pins.
• Chassis Ground Point (Rear) — There are several main earth points. A key one is located on the chassis leg in the rear of the vehicle, near the suspension and fuel tank mounting points.. A corroded or loose rear ground point can cause an intermittent or total loss of power to the additive pump, leading to P1437 and related communication faults.
• Wiring Harness Chafe Point — The wiring loom running from the BSI to the additive pump is often clipped to the underbody or routed over the rear axle. These clipping points or areas of movement are common locations for wires to chafe through their insulation over time.. A short-to-ground or an open circuit in the harness due to chafing will cut power or communication to the pump, directly causing this fault. A visual and continuity check of the loom is critical if the connector itself looks clean.

Real Owner Repair Stories

• YouTube user comment / Forum posts (Peugeot/Citroen with 1.6/2.0 HDi engine) — Persistent 'Depollution System Faulty' message with codes P1434 and P1435 (pump and communication fault).
  ❌ Tried (didn't work) Replacing the DPF additive pump/tank assembly.
  ✅ What actually fixed it The fault persisted after replacing the pump. The actual cause was found to be corroded and broken wires in the harness about 30cm away from the pump connector. Repairing this section of the wiring loom finally cleared the codes.
• Honest John Forums (2005 Peugeot 407 2.0 HDi) — P1435, P2408 (Fuel Cap Sensor), and P0461 (Fuel Level Sensor) all appearing together.
  ❌ Tried (didn't work) Clearing codes (they would return)., Checking additive level (it was half full)., Confirming pump operation (it was heard priming after cycling the fuel cap).
  ✅ What actually fixed it The user suspected a faulty additive ECU was causing the cluster of related faults, as individual components like the pump and cap sensor appeared to be working when tested in isolation. The final fix was not posted, but the diagnosis pointed towards the central controller being the root cause after ruling out the more common component failures.

OEM Part Supersession History

• Various older numbers (e.g., 1500.NK) → 9672419980 — Consolidation of part numbers for the complete pump and tank assembly for non-Euro 6 vehicles.
  Heads up: This part number is specifically for pre-Euro 6 vehicles. It is not compatible with later 'BlueHDi' models which use a different system. Always verify compatibility with the vehicle's VIN before ordering.
• Eolys 176 → Infineum F7995 — Change in fluid formulation by the supplier. They are considered interchangeable for the same application.
  Heads up: Do NOT mix with earlier DPX 42 fluid or later Eolys Powerflex/Extend fluids. The correct fluid type is determined by the vehicle's ORGA/DAM number, not just the model year.

Model Year Variations Within This Range

• 2004-2011 (Varies by build date): The type of Eolys fluid required. The specific fluid is determined by the vehicle's ORGA (or DAM) number, found on the driver's door jamb sticker. For the 407, vehicles with ORGA numbers from 9493 up to 12075 typically use Eolys 176 or its replacement, Infineum F7995. Vehicles from ORGA 12076 onwards may use Eolys Extend. Using the wrong fluid can cause system malfunctions.
• Approx. 2008 onwards: On later models, the separate, dedicated additive ECU was often eliminated. Its functions were integrated directly into the main BSI (Body Systems Interface) and the Engine ECU. This changes the diagnostic path in Diagbox, as you will no longer find a separate 'Additive ECU' to communicate with; instead, configuration and resets are done within the BSI or Engine ECU menus.

Diagnostic Flowchart

Other Known Issues on This Vehicle

Issues unrelated to this code that are worth knowing about as an owner of this generation:

• Dual-Mass Flywheel (DMF) Failure 🔴 High — Common after 80,000-120,000 miles. Symptoms include rattling/knocking noise at idle that may disappear when the clutch is pressed, and vibrations through the clutch pedal and chassis.
• Heater Flap Actuator Failure 🟠 Medium — Very common. The plastic gears or shafts for the dual-zone climate control flaps break, causing one side to blow hot air and the other cold, regardless of settings. Repair kits are available.
• Lower Ball Joint Wear 🟠 Medium — Front lower ball joints are a known weak point, wearing out prematurely and causing a 'clunking' or 'knocking' sound from the front suspension over bumps or at low speeds.
• COM2000 / Steering Column Switch Unit Faults 🟡 Low — The integrated switch unit (COM2000) behind the steering wheel can develop internal faults, leading to erratic behavior of indicators, headlights, wipers, or causing spurious airbag warnings.
• Intake Manifold Swirl Flap Issues 🟠 Medium → Shop Engine Intake Manifold — The plastic swirl flap actuator or the flaps themselves can wear or break, leading to rough running, hesitation, and fault codes related to the intake system.
• Electrical Gremlins (BSI/Connectors) 🟠 Medium — General electrical issues can arise from the Body Systems Interface (BSI) or from corroded connectors, causing a wide range of unpredictable symptoms from warning lights to non-starting conditions.

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: A used pump and tank assembly from a salvage yard can be a viable, cost-effective option, especially if the failure is confirmed to be the pump's electronics and not just an empty tank. It is a good choice if the donor vehicle is a low-mileage, rear-end collision.

Donor-vehicle mileage cap: roughly under 80000 miles for the part to have meaningful remaining life.

What to inspect on the donor part:

• Check for zero corrosion on the electrical connector pins.
• Inspect the plastic tank for any cracks or signs of past leaks.
• Ask the dismantler if they know the history or if the fluid level is known. A full tank is a bonus.
• Ensure all hose connection points are intact and not broken.

OEM-only on this vehicle (don't cheap out):

• While not strictly 'OEM-only', the Eolys fluid itself should be from a reputable manufacturer (like Walker) that guarantees compatibility (e.g., Eolys 176, Infineum F7995). Avoid 'universal' DPF fluids.

Aftermarket brands forum-validated for this vehicle:

• VDO (often the original equipment manufacturer)
• Meat & Doria
• Hoffer
• Walker (for Eolys fluid)

Brands owners have reported issues with on this vehicle:

• Unbranded, no-name pump assemblies from online marketplaces are a significant risk due to potential communication issues with the vehicle's CAN bus system.

Real Owner Stories

Aggregated from forums and TSBs cited above. Mileages and costs reflect what owners reported in those sources.

Related OBD-II Codes

• P1434 — Additive Pump Fault. This code, along with P1435, is often found with P1437 and points directly to a failure in the additive pump's motor or electrical circuit.
• P1435 — Additive Pump Fault. This code, along with P1434, is often found with P1437 and points directly to a failure in the additive pump's motor or electrical circuit.
• P1445 — Additive Level Low. This code indicates the calculated amount of Eolys fluid is at or below the minimum threshold. An empty tank is a primary cause for the system to log fault P1437.
• P2408 — Fuel Cap Sensor Circuit Fault. The additive system relies on this sensor to know when the car has been refueled. If the sensor fails, the pump won't dose fluid, eventually leading to a system fault like P1437.
• U0118 — Lost Communication With Fuel Additive Control Module. This indicates a complete communication breakdown, often due to damaged wiring, a corroded connector, or a failed module, all of which are root causes for P1437.
• P1471 — A related DPF system code. A forum user fixed this code by repairing a poor electrical connection, which is a common cause shared with P1437.

Frequently Asked Questions