AdBlue Fault Code Lookup: What P20EE, P204F, P20E8, P207F & P2002 Mean
I Fix AdBlue | November 2025
Quick Reference: Common AdBlue Fault Codes
| Fault Code | What It Means | Common Cause | Urgency Level |
|---|---|---|---|
| P20EE | NOx catalyst efficiency low | Failing NOx sensor or AdBlue dosing issue | High – triggers countdown |
| P204F | AdBlue system performance fault | Faulty pump, blocked injector, or contamination | Critical – no-start risk |
| P2002 | DPF efficiency below threshold | Failed regen due to AdBlue system fault | Medium – affects performance |
| P20E8 | AdBlue (reductant) pressure too low | Weak pump, clogged filter, leaking line or injector, frozen fluid, low voltage at the pump | High – triggers countdown |
| P13DF | AdBlue heater circuit fault | Heater failure (common in winter) | High – winter no-start risk |
Introduction
Modern diesel vans and cars use AdBlue (SCR) systems to cut NOx emissions. When something goes wrong, the ECU logs fault codes and often puts the vehicle into limp mode or even starts a “no start” countdown.
If you’ve just scanned your vehicle and seen codes like P20EE, P204F or P2002, this guide will help you understand:
- What each common AdBlue‑related code actually means
- Typical causes in the real world
- What usually fixes it
- Where to read more about repairs, deletes and UK‑typical costs
Thinking of clearing the code yourself? Read Can you clear or reset an AdBlue fault code? further down first.
This page tells you what a code means. If you already know that and need to find what is actually causing it on your van, work through our AdBlue fault diagnosis guide. It covers the live data checks that separate a fluid, pressure, sensor or wiring fault.
How AdBlue Fault Codes Work
The ECU constantly monitors sensors around the AdBlue and exhaust system – NOx sensors, temperature sensors, pressure sensors, AdBlue level and pump performance. When readings go outside the expected range, it stores a diagnostic trouble code (DTC).
Some codes are “soft” and only light the engine warning lamp. Others are “hard” and will:
- Trigger limp mode
- Start a countdown such as “0 miles until no start”
- Prevent the engine from starting once the countdown hits zero
If you’re already in a countdown situation, this article pairs well with how to clear a no‑start countdown without the dealer .
Pending, stored and permanent codes
Your reader may label a code pending, stored or permanent, and the label tells you how far the fault has gone.
- Pending: the test failed once but has not repeated enough for the ECU to act on it.
- Stored (confirmed): it has repeated, and the ECU now treats it as a real fault. This is usually when the warning light comes on.
- Permanent: the ECU wants to see the fault fixed and the test passed before it will let the code go. A scan tool or a battery disconnect will not clear it.
Key AdBlue‑Related Fault Codes
Why your scanner shows P204F00, P204F‑09 or P204FFD: many scan tools add two extra characters to the end of the code, so the same fault can appear several ways. The first five characters are the standard fault code, and they are what the explanations below are based on. The extra two are a sub-code the manufacturer’s software uses to say more about how the fault was detected. They vary by make and scan tool, so look up the first five characters.
P20EE – SCR NOx Catalyst Efficiency Below Threshold
What it means: The ECU thinks the SCR catalyst isn’t reducing NOx emissions effectively.
Typical causes:
- Failing or contaminated SCR catalyst
- Faulty NOx sensor giving incorrect readings
- AdBlue dosing problems (pump or injector)
- Long‑term driving with other AdBlue faults present
What usually fixes it:
- Check and, if needed, replace the NOx sensor
- Test AdBlue pump and injector performance
- In severe cases, replace the SCR catalyst
For help deciding whether to replace the NOx sensor or look at delete options, see NOx sensor delete vs replacement and signs your NOx sensor is failing .
P204F – Reductant System Performance (P204F00, P204FFD)
What it means: The AdBlue (reductant) system as a whole isn’t performing as commanded. The ECU asked for dosing, and the result, usually pressure or NOx reduction, didn’t match what it expected.
Typical causes:
- Low‑quality or contaminated AdBlue
- AdBlue pump not delivering enough pressure
- Blocked or sticking AdBlue injector
- Frozen or crystallised AdBlue in pipes
- SCR catalyst starting to fail
What usually fixes it:
- Drain and refill with fresh, good‑quality AdBlue
- Test and, if needed, replace the pump or injector
- Flush the system if crystals or contamination are present
We cover real‑world fixes for repeated AdBlue failures in why your AdBlue system keeps failing again and again .
Seeing P204F00 on an Audi? Our Audi AdBlue warning light guide covers the Audi-specific patterns and the no-start counter.
P20E8 – Reductant Pressure Too Low
What it means: The AdBlue (reductant) system can’t build or hold the pressure the ECU expects, so dosing is cut back and the warnings start. Left alone, it can lead to limp mode or a no‑start countdown.
Typical causes:
- Worn or failing AdBlue pump
- Clogged filter or pickup from crystals or contaminated fluid
- Frozen or gelled fluid after a cold night, before the heater has done its job
- A leaking line or injector, so pressure drops when dosing starts
- Electrical faults: low battery voltage, a poor earth, a corroded connector or a failed pressure sensor
What usually fixes it:
- A prime and pressure test comparing target and actual pressure, before any parts are changed
- Repairing the wiring, connector or leak the test points to
- Replacing the pump only when it can’t hold pressure with a good electrical supply
P20E8 often turns up alongside P204F, because low pressure is one of the most common reasons the system can’t perform as commanded.
P2002 – DPF / NOx Trap Efficiency Below Threshold
What it means: The DPF or NOx trap isn’t cleaning exhaust gases properly.
Typical causes:
- Blocked or overloaded DPF
- Short‑journey driving preventing regeneration
- Sensor faults around the DPF or exhaust
- Issues upstream in the AdBlue or EGR systems
What usually fixes it:
- Proper DPF clean or regeneration
- Repairing any AdBlue or EGR faults that caused the overload
- In some cases, DPF replacement or a DPF delete solution
If you’re weighing up long‑term options on a high‑mileage work van, our AdBlue delete vs repair guide and the DPF solutions at Leicester Remaps are useful next reads.
P207F – Reductant Quality
What they mean: The ECU has detected a problem with AdBlue quality, concentration or level.
Typical causes:
- AdBlue mixed with water, diesel or dirt
- Very old AdBlue that has degraded
- Level sensor mis‑reading the tank
- A blocked or crystallised injector, so the dose is wrong even with good fluid
- Unsteady pump pressure
- A NOx sensor that reads wrong, so the ECU blames the fluid
- A faulty tank temperature reading, which throws the dosing calculation out
What usually fixes it:
- Drain the tank and refill with fresh, branded AdBlue
- Clean or replace the level/quality sensor if readings stay wrong
For a deeper look at contamination and real‑world fixes, see urea delete and real‑world fixes .
If fresh, branded AdBlue from a sealed container hasn’t cleared P207F, the fluid probably wasn’t the problem.
P203F – Level Sensor Circuit (Tank Reads Empty When It’s Full)
What it means: P203F is about the signal from the level sender inside the AdBlue tank, not about how much fluid is in it. When that signal goes outside the range the ECU expects, the code sets. That is why it often survives a fill-up.
How to tell a real low level from a sensor fault:
| Genuine low level | Level sensor circuit fault | |
|---|---|---|
| Warning | Builds gradually, with a range or countdown | Appears suddenly, often with no countdown |
| After filling | Clears within a drive cycle | Stays on or comes back quickly |
| Codes | Usually none, or a level warning only | P203F or another P203x code |
| Pattern | Steady | Comes and goes, often with temperature |
Typical causes, most common first: a failed level sender in the tank, a corroded or wet connector on top of the tank, chafed wiring between the tank and the SCR module, a poor earth shared with other SCR parts, or frozen or crystallised fluid around the sender.
What usually fixes it: read live level data against what is actually in the tank, then test supply, earth and signal at the sender plug. Only replace the sender once the wiring has been proven good.
MOT: on diesels first used from 1 July 2008, an engine warning light that is on is a major defect, so a stored P203F that lights it will fail the test (MOT inspection manual, section 8.2.2.2).
P2200–P2202 – NOx Sensor Circuit Faults
What they mean: The ECU can’t communicate properly with a NOx sensor.
Typical causes:
- Failed NOx sensor
- Damaged wiring or corroded connector
- Water ingress in the loom
What usually fixes it:
- Check wiring and connectors for damage
- Replace the affected NOx sensor
- Clear codes and road‑test to confirm
Because NOx sensors are expensive, many owners compare replacement with NOx sensor delete options .
U029D – Lost Communication With the NOx Sensor
What it means: U-codes are communication faults. U029D says the ECU has lost contact with a NOx sensor module. It does not mean the sensor is giving a bad reading.
Typical causes, in the order to check them: a wet or corroded connector or loose pins (start here if it shows up after rain or washing), harness damage where it rubs on brackets or heat shields, a weak supply or poor earth that makes the module drop off the network, and last of all the sensor module itself.
Why it matters: if the ECU can’t hear the NOx sensor, it can’t check the SCR system is working. Warnings, and later a countdown, can follow even when the rest of the system is fine.
P2BAE / P2BAF – SCR NOx Exceeded Limit
What they mean: The vehicle has exceeded allowed NOx emissions despite AdBlue dosing.
Typical causes:
- Combination of NOx sensor and SCR efficiency issues
- AdBlue dosing problems plus high‑load driving
- Long‑term running with other unresolved AdBlue faults
What usually fixes it:
- Address any underlying P20EE/P204F/P2002 codes first
- Verify correct AdBlue dosing and SCR operation
Can You Clear or Reset an AdBlue Fault Code?
Short answer: you can clear it, but it will come back unless the cause is fixed. Clearing a code only removes the warning for now. The ECU runs the same checks next time the van starts or drives, and if the readings are still wrong the code returns. That is why the warning comes back after a basic scanner clear or a battery disconnect.
Check these before you clear anything:
- Photograph the dash message, and the miles left if there is a countdown.
- Read and write down every code, not just the one the dash mentions.
- Check whether the code is active now or only stored from before.
- Confirm the AdBlue came from a sealed container, and note how long after a refill the fault appeared.
- Look for white crystals around the injector and lines.
A reset will not hold if: a sensor is still sending bad readings, the pump or injector is still underperforming, SCR efficiency is still below the threshold, or the no-start countdown is already active. A reset is the last step after the fault is fixed, not a replacement for finding it.
Can I reset it without a scanner? On most vans, no. Disconnecting the battery does not clear an AdBlue fault or a countdown, and permanent codes need the repair confirmed first. If you’re in a countdown, see how to clear a no-start countdown without the dealer.
What Happens If You Ignore AdBlue Fault Codes?
Ignoring AdBlue‑related codes can lead to:
- Repeated limp mode events
- “0 miles until no start” countdowns
- Permanent no‑start until the system is repaired and reset
- Long‑term damage to the SCR catalyst or DPF
If you’re already seeing a no‑start countdown, read how to clear a no-start countdown without the dealer for immediate next steps.
Typical UK Cost Ranges (Guide Only)
These figures are general UK market ranges to help you understand the scale of repairs. They are not specific prices for any one garage or provider. For a full breakdown by fault type, see our complete AdBlue repair cost guide .
- Diagnostic scan: around £50–£120
- AdBlue drain and refill: around £150–£300
- NOx sensor replacement: often £300–£550
- AdBlue pump replacement: often £400–£700
- SCR catalyst replacement: often £600–£1,200
Repair vs Delete – Which Route Makes Sense?
On newer, low‑mileage vehicles, repair is usually the obvious choice. On older, high‑mileage work vans, repeated AdBlue and NOx‑related codes can become an expensive cycle of parts and labour.
Many owners compare long‑term repair costs with:
- AdBlue delete vs repair – what’s right for your van?
- Can you still pass an MOT after emissions deletes?
Before deciding, it’s important to understand the legal and MOT position. Our article AdBlue delete legal UK explains the current situation in detail.
Related Guides
- AdBlue fault diagnosis – finding the real cause
- Why your AdBlue system keeps failing again and again
- What causes AdBlue faults and how to fix them
- AdBlue repair vs delete
- AdBlue problems – service overview
Need Help With an AdBlue Fault Code?
If your scan tool is showing one or more of these codes and you’re not sure what to do next, the safest option is a proper diagnostic session with someone who specialises in AdBlue, NOx and SCR systems.
We offer mobile diagnostics and AdBlue solutions across Leicester and the surrounding areas. You can get in touch via the contact us page, or browse our AdBlue delete and AdBlue problems service pages for more information.
