Diagnosing and Repairing MK1 E3 AdBlue Faults – Citroën & Peugeot
AdBlue is a key component in reducing emissions on modern PSA diesel vehicles, introduced to meet Euro 6 standards by lowering harmful nitrogen oxide (NOₓ) output. The MK1 E3 AdBlue (Diesel Exhaust Fluid) system is used across a range of Citroën and Peugeot models, including the Citroën C-Elysee, C3 II, C3 Picasso, C4 Cactus, DS3, and the Peugeot 2008 I, 208 I, and 301. This system injects AdBlue into the exhaust to convert NOₓ into harmless nitrogen and water vapour. If the system develops a fault, it can lead to dashboard warnings, reduced engine performance, or complete engine immobilisation if left unresolved.
Common Faults:
- Internal corrosion or water ingress
- Short circuits or internal electrical faults
- Crystallisation of AdBlue fluid around the injector or level sensors
- Faulty temperature, level, or quality sensors within the tank
- P20E9 00 Fault Code – AdBlue/DEF Fluid Pressure: Drift Upwards
Common Faults and Diagnosis
Fault Code P20E9 00: AdBlue/DEF Fluid Pressure Drift Upwards
Fault code P20E9 00 indicates that the AdBlue (Diesel Exhaust Fluid) pressure in the Selective Catalytic Reduction (SCR) system has risen beyond its normal operating range. In vehicles equipped with the MK1 E3 AdBlue system—used across various Citroën and Peugeot models—this issue is typically caused by a failing high-pressure pump, crystallised return lines, contaminated fluid, or a faulty pressure sensor that inaccurately reports data to the ECU.
Why the Pressure Drift Happens
The MK1 E3 system relies on precise dosing of AdBlue into the exhaust stream to ensure effective NOₓ reduction. If pressure builds up—often due to a blocked valve, degraded pump seals, or internal component wear—it can lead to over-injection of fluid. This causes crystallisation in the dosing module, potential injector damage, and a decline in system performance.
Symptoms and Driving Impact
When P20E9 00 is triggered, the vehicle may display warnings such as “Emission Control Fault” or “Check Urea System”. While driveability might not be affected at first, the system will eventually activate limp-home mode, reduce engine power, and initiate a mileage countdown. If the fault is not resolved, the vehicle may refuse to start altogether.
Diagnostic Procedure and Repair Advice
A full diagnostic scan using PSA-compatible tools will confirm fault P20E9 00 and reveal any associated freeze-frame data. Inspection should include the high-pressure pump, return lines, dosing injector, and pressure sensor. The AdBlue fluid itself should be checked for contamination or incorrect concentration, which can also trigger system malfunctions.
Essex Recons Repair Services
At Essex Recons, we specialise in the refurbishment of MK1 E3 AdBlue systems found in a range of Citroën and Peugeot diesel models. Each unit undergoes complete disassembly, ultrasonic cleaning, replacement of worn components, and thorough pressure testing. Our goal is to return your SCR system to full functionality, keeping you compliant with Euro 6 emissions standards.
Part Numbers
9818703780, 9812914780, 9808559680, 1682620380, 16 826 203 80, 98 129 147 80, 98 187 037 80, 1682615880
Affected Vehicles - Shop Now
Citroën
Peugeot
Common Questions:
We at Essex Recons strive to exceed your expectations in the quality of our repairs. We aim to complete our repairs in a timely fashion while adhering to all ESD safety measures when working on sensitive equipment.
These units come with a lifetime* warranty.
To pay for the rebuild, simply click the product link(s) above to select the module you require. After that, place your order directly through our website. Once your order is complete, carefully package your unit inside a sturdy box with plenty of protective material. In addition, make sure you include your contact details and order number inside the box. Then, send your package to us using a tracked courier service. As soon as we receive your unit, we will test, rebuild, and return your module, complete with your warranty.
Yes! Once an order has been placed you can drop your unit off at the following address: Unit H, OYO Business Units, Hindmans Way, Dagenham, Essex, RM9 6LN, UK. Quote your order number at the till to ensure a smooth dropoff!