Mobile AdBlue and NOx specialists
AdBlue fault codes.
What each one means.
P20EE, P20E8, P204F, P229F and the rest, explained without the jargon. Send us the code with your reg for a fixed quote.
At home or work. Clear advice. A price agreed before work starts.
7 days a weekSame-day visits where available213 AdBlue faults fixed since May 2026
Let's get you moving
Tell us about your vehicle.
Enquiry received, thank you.
We will text your quote shortly. If it is urgent, call 0207 046 1823.
Our process
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1
Diagnose
Full diagnostics of the emissions system at your vehicle
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2
Attempt repair
Software repair and re-initialisation of the control modules
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3
Bypass
If necessary, a permanent bypass or deletion with a lifetime warranty
Start with your symptom
What’s happening with your vehicle?
Quick Reference
The Ten AdBlue Codes We See Most
What the code means, what usually sets it, and what actually makes it stay off. Send us the code with your reg for a fixed quote by text.
Usual cause
A crystallised dosing injector, low dosing pressure or a lazy downstream NOx sensor; the catalyst itself is rarely the first cause
Your options
Dealer route: injector, pump or catalyst, often more than one visit. Our fix: diagnose the real cause, then the permanent software fix, same day
Usual cause
Worn pump, blocked line or a crystallised injector holding the pressure down
Your options
Dealer route: pump, or the whole sealed tank module on most vans. Our fix: the permanent software fix, no parts to wait for
Usual cause
Blocked injector or return line
Your options
Dealer route: injector clean or replacement. Our fix: the permanent software fix
Usual cause
A dosing or quality problem sitting behind another code
Your options
Clears with the primary code once that is fixed; on its own it never needs a part
Code
P207F
Reductant quality performance
Usual cause
Contaminated or stale fluid, or a quality sensor reading wrong
Your options
Often just stale or wrong fluid: drain and refill, which any garage can do. If the quality sensor has failed, our software fix
Usual cause
Tank heater open circuit, usually sealed into the tank unit
Your options
Dealer route: the sealed tank unit, a four-figure part for a few cold weeks a year. Our fix: the permanent software fix
Usual cause
Upstream sensor or its loom
Your options
Dealer route: NOx sensor, £300 to £600 fitted. Our fix: the permanent software fix, lifetime warranty
Usual cause
A drifted upstream sensor
Your options
As P2200. We confirm which sensor with live readings before anything is done
Usual cause
A drifted downstream sensor
Your options
As P2200. We confirm which sensor with live readings before anything is done
Code
U029D
Lost communication with NOx sensor
Usual cause
Loom, connector or sensor power supply
Your options
Usually a loom or connector, not the sensor. We show you the reading; it is a cheap job for any garage, and no reason to buy a sensor
Reading the Code
Why One Code Rarely Means One Part
An AdBlue fault code tells you which test the engine control unit failed, not which part is broken. P20EE says the catalyst is not reducing NOx as expected. That can be the catalyst, but far more often it is a crystallised injector or weak dosing pressure upstream, and the downstream sensor is simply reporting the result.
Codes also cascade. Low dosing pressure sets P20E8, the catalyst then under-performs and P20EE joins it, and a system-performance code such as P204F gets logged on top. Replace the catalyst at that point and the pressure fault is still there. Two visits and two bills for one problem.
This is why we read the freeze-frame data behind the code and run the live tests before recommending anything. See exactly what we test at your vehicle.
Our Approach
How We Confirm It, Then Fix It
The diagnostic visit reads every stored code with its freeze-frame data, then checks the system live: dosing pressure against the commanded value, both NOx sensors with the engine running, heater current draw, fluid quality against the quality sensor, and the injector, wiring and connectors. The readings tell us which code is the cause and which are symptoms.
Then you get the honest answer. We do not fit parts, so we have nothing to sell you: if the readings show stale fluid or a corroded connector, we tell you, and any garage can sort it. If a component has genuinely failed, you see the reading and what a dealer would charge for the part, and our permanent software fix clears the fault at source with a lifetime warranty.
The diagnostic visit is £185 and includes control module resets and re-initialisation. Go ahead with the full fix on the day and it is included in the from-£250 price.
- Every code read with freeze-frame data, not just the headline code
- Live-data tests before anything is recommended
- We do not fit parts, so the advice is straight
- Fixed price before any work starts, nothing to pay up front, lifetime warranty on the fix
How it works
A clear route to the right solution.
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01
Tell us the symptoms
Give us a few details about your vehicle and the issue.
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02
We diagnose at your location
Our mobile technician comes to you with the right equipment.
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03
You approve the next step
We explain the findings and agree the way forward.
Our pricing
Clear pricing. No surprises.
Diagnostic visit
£185
Fault-code and live-data checks, control module resets and written findings. Included if you go ahead with the full fix on the day.
AdBlue software service
From £250
Diagnostics included. Lifetime warranty on the work. Vehicle and use eligibility checked first.
ECU unlocking, where required, is quoted separately before work starts. What the lifetime warranty covers.
Get a fixed quoteFAQ
AdBlue Fault Codes: Your Questions Answered
The ten above cover the large majority of AdBlue, SCR and NOx faults we see. Makes also use their own codes, for example P13DF on Mercedes or P1434 and P1435 on Peugeot and Citroën additive systems. Send us whatever code you have with your registration and we will tell you what it means.
You can clear it with a code reader, but the fault is still logged in the system and the code returns within a drive cycle or two. If a countdown has started it carries on. Clearing codes without fixing the cause can also hide freeze-frame data we would use to diagnose it.
Because the cause has not been fixed. A returning P20EE usually means the injector or dosing pressure upstream was never addressed, and a returning NOx code often means the wrong sensor was replaced. Live-data testing finds which it is.
No. We read manufacturer-level codes and live data at your vehicle with the same depth as a dealer, at your home or workplace, 7am to 8pm, 7 days a week.
The diagnostic visit with control module resets is £185. The full permanent software fix is from £250 with the diagnostic included. We do not fit parts; if the diagnostic shows something a garage should do instead, we tell you and you pay only for the visit.
Let’s work out what your vehicle needs.
Speak to a specialist or request your free quote.