Why AdBlue Fault Codes Keep Appearing
Modern vans use AdBlue and SCR systems to cut emissions. When these systems go wrong, the ECU stores fault codes and switches on warning lights. For drivers, that often means limp mode or a countdown to no-start. If you’re seeing codes on your scan tool or dash, here’s what they mean and how to clear them.
Common AdBlue Fault Codes on Vans
Different makes use different codes, but the problems are similar. Here are the ones we see most often:
- P20EE: SCR system efficiency below threshold.
- U029D: Lost communication with NOx sensor.
- P229F: NOx sensor stuck or giving invalid readings.
- P204F: Reductant system performance fault.
- P2BA9: SCR NOx catalyst efficiency issue.
Each of these codes points to a part of the AdBlue system failing — sensors, pumps, heaters, or wiring.
What Triggers These Faults?
There are a few repeat causes across most vans:
- Blocked AdBlue dosing lines or injectors.
- Failed NOx sensors sending false signals.
- Pumps that no longer deliver enough pressure.
- Frozen AdBlue tanks damaging heaters in winter.
- Wiring corrosion stopping modules from talking to each other.
When any of these happen, the ECU locks in a code and puts the van into a reduced power mode.
How to Reset AdBlue Fault Codes
Clearing the code is not always enough. The ECU checks live data every time you start the engine. If the underlying fault remains, the code will return. The steps usually are:
- Run diagnostics with a scan tool to read codes.
- Fix the fault — replace the sensor, reset the pump, or repair wiring.
- Clear the code and test drive to confirm it does not return.
In some cases, the only permanent fix is a software solution such as an AdBlue delete service.
Can You Clear Codes Yourself?
Basic OBD tools can read and clear codes, but they won’t fix the fault. You may clear the warning, only for it to return within miles. Professional equipment is needed to reset AdBlue systems fully.
How Much Does It Cost to Fix AdBlue Faults?
The cost depends on the part at fault:
- NOx sensors: £350–£650 each.
- AdBlue pumps: £900–£1,500 at main dealers.
- Heaters and tanks: £400–£700 depending on make.
- Software delete: £300–£500 one-time fix.
This is why many van owners choose to remove the system rather than keep replacing costly parts.
AdBlue Fault Codes on Popular Vans
We regularly see the following:
- Mercedes Sprinter: P20EE and countdown resets are common.
- Ford Transit: AdBlue malfunction with no stored codes is a frequent complaint.
- Peugeot Boxer / Citroën Relay: U029D communication errors with the NOx sensor.
These repeat faults show how widespread AdBlue system failures are across UK fleets.
Delete vs Repair – Which Makes Sense?
If you need to keep the van standard for fleet contracts or resale, repair may be best. If downtime and repeat costs are a bigger problem, a delete can stop codes returning for good. You can read more about system repairs on our SCR system repair page.
Book a Mobile Fix
We diagnose, reset, and clear AdBlue fault codes across Leicester and nearby counties. Same-day and next-day visits are often available. We use dealer-level equipment and safe software solutions.
Want those codes gone? Call 07349 821 999 or email info@ifixadblue.co.uk now to book.
Hours: Monday–Sunday, 09:00–20:00
