Common AdBlue Fault Codes We See on Vans

Fault code numbers vary by manufacturer, but the underlying issues are often the same. These are some of the most common SCR and AdBlue-related codes we encounter:

• P20EE – SCR system efficiency below threshold
• U029D – Lost communication with NOx sensor
• P229F – NOx sensor implausible or out-of-range readings
• P204F – Reductant system performance fault
• P2BA9 – SCR catalyst efficiency issue

These codes are not random. They point to how the ECU is interpreting sensor data and SCR system behaviour, not just whether a single component has physically failed.

What Usually Triggers These Fault Codes

In real-world use, AdBlue fault codes are most often triggered by data or logic issues inside the SCR system. Common causes include:

• NOx sensors sending implausible or inconsistent readings
• SCR efficiency checks failing during normal driving
• AdBlue dosing data not matching ECU expectations
• Communication issues between SCR control modules
• Software adaptations drifting outside acceptable limits

When this happens, the ECU logs a fault and may limit performance or start a countdown. Even if the vehicle still drives normally, the system remembers the condition and will often bring the warning back.

Why Clearing the Code Often Doesn’t Work

Clearing an AdBlue fault code only removes the warning temporarily. Every time the engine starts, the ECU re-checks live data from the SCR system.

If the readings still fall outside expected values, the code returns — sometimes immediately, sometimes after a short drive cycle.

This is why many drivers see the same warning reappear even after:

• resetting the code with a scanner
• disconnecting the battery
• having the warning cleared at a garage

How AdBlue Fault Codes Are Dealt With

There are generally three routes when AdBlue fault codes keep returning:

1. Software reset and adaptation checks

In some cases, a software reset and adaptation correction is enough to stop a warning returning, especially if the fault was triggered by temporary or incorrect data.

2. Ongoing repair route

Drivers who want to keep the factory emissions system active may choose to pursue repairs through a garage or dealer. This usually involves identifying which sensor data is triggering the code and deciding whether replacement work is worthwhile.

3. AdBlue delete (off-road / export use)

An AdBlue delete is a software-only solution that disables SCR and AdBlue logic inside the ECU. This removes the conditions that trigger warnings, limp mode, and no-start countdowns.

This option is intended for off-road, motorsport, or export vehicles and is not for UK road use.

Can You Clear AdBlue Fault Codes Yourself?

Basic OBD tools can read and clear codes, but they do not change how the ECU evaluates SCR data. As a result, warnings often return within miles or after the next restart.

Professional equipment is required to properly assess live data, reset adaptations, or apply software-level solutions where appropriate.

Why Many Vans End Up With Repeat AdBlue Faults

The SCR system relies on multiple inputs working together. If one value drifts or conflicts with others, the ECU may flag a fault even when the vehicle still runs.

That’s why many vans experience a cycle of:

• warning appears
• code is cleared
• warning returns days or weeks later
• countdown eventually starts

Once this pattern begins, drivers often look for a more permanent solution.

Book Mobile Help for AdBlue Fault Codes

We provide mobile diagnosis, software resets, and AdBlue delete solutions where suitable. We don’t replace parts or carry out physical repairs.

Based in Leicester, we cover Leicestershire and the Midlands, including Coventry, Derby, and Nottingham. Same-day visits are often available.

• Phone: 07349 821 999
• Email: info@ifixadblue.co.uk
• Hours: Monday–Sunday, 09:00–20:00