P20EE fault code meaning and fix
P20EE means the AdBlue system isn't bringing NOx emissions down as far as the engine computer expects. A failing NOx sensor, poor-quality AdBlue or a crystallised dosing injector is usually behind it, and we can read the system at your home or workplace to find which.
The short answer
The official description for P20EE is SCR NOx catalyst efficiency below threshold (bank 1). SCR stands for selective catalytic reduction, the part of the exhaust where AdBlue turns NOx into nitrogen and water. The ECU compares the NOx sensor reading before the catalyst with the one after it, and P20EE sets when the drop between them is too small.
You can usually keep using the vehicle for now, but don't sit on it. On Euro 6 diesels a lasting AdBlue fault starts a countdown, and once that reaches zero the engine won't restart after it's switched off.
Symptoms that go with P20EE
- The engine management light, often with an AdBlue or emissions warning on the dash
- A dash message counting down to a no-restart
- AdBlue use that looks higher or lower than you're used to
- White crusty deposits around the AdBlue injector or exhaust joints
What causes P20EE
| Cause | What you might notice | How it's confirmed |
|---|---|---|
| Failing NOx sensor before or after the catalyst | Code returns soon after clearing, readings that don't move | Live NOx readings compared upstream and downstream |
| Diluted, old or contaminated AdBlue | Code set soon after a top-up from an unfamiliar bottle | Quality reading on live data, a look at the fluid |
| Crystallised or blocked AdBlue injector | White deposits around the injector | Dosing test and injector readings |
| Low dosing pressure from the AdBlue pump | Pressure codes such as P20E8 alongside | Pump pressure on live data |
| Worn or contaminated SCR catalyst | Code keeps returning with healthy sensors and dosing | Ruling out every other cause first |
| Exhaust leak ahead of a NOx sensor | Blowing sound, soot marks at a joint | Visual check and sensor plausibility |
Reading P20EE properly
P20EE is a generic code, so it points at the same SCR catalyst test on every make. Scanners often show it as P20EE00 or P20EE92, and those two extra characters are a sub-code that narrows the fault down without changing what the main code means.
P20EE only reports the end result, NOx leaving the exhaust too high. The cause could sit anywhere upstream, so the freeze-frame record and any other stored codes are what point towards a sensor, the fluid or the dosing side.
How P20EE gets fixed
Read every code and the AdBlue status
Stored and pending codes, NOx sensor readings, dosing pressure and the countdown figure all come off the ECU.
Narrow it down
Sensor readings are compared before and after the catalyst, and the dosing system is tested to see whether the right amount of AdBlue is going in.
Repair the cause
A dealer or a garage that handles SCR systems replaces the sensor, injector or pump we've identified.
Clear and recheck
Once the part is replaced, the code is cleared and the system is run again to confirm the NOx reduction is back where it should be.
What we can do about P20EE
Mobile diagnostics, £100 + VAT
We read the codes, NOx readings and AdBlue status where the vehicle is parked and tell you which part has caused P20EE. We don't repair AdBlue systems, so you leave with a clear answer for your dealer or SCR specialist.
AdBlue delete, £330 + VAT
A software delete removes the AdBlue system's control from the ECU, so the SCR test no longer runs.
What does P20EE mean in plain English?
The AdBlue part of the exhaust isn't cleaning up as much NOx as it should, so the engine computer has logged a fault and lit the warning light.
Is P20EE a serious fault?
It won't harm the engine directly, but the no-restart countdown makes it serious for anyone who relies on the vehicle. Leaving it until the counter is low risks being stranded.
Can I clear P20EE with a cheap code reader?
The light may go out for a few journeys. The ECU repeats the NOx comparison every time conditions allow, so a cheap reader can't stop it returning, and on many vehicles it can't reset the countdown either.
Is P20EE any different on a Peugeot?
The code means the same thing on a Peugeot as on any other make. Some Peugeot and Citroen scanners add a sub-code such as 92, which adds detail but still points at the SCR system.
How much does it cost to find the cause of P20EE?
A mobile diagnostic is £100 + VAT, carried out at your home or workplace. It shows whether you're looking at a sensor, the fluid or the dosing side before you spend money on parts.
Who is the AdBlue delete for?
It's sold for off-road and export vehicles only, so it isn't a fix for P20EE on a road car or van. Read Is AdBlue delete legal? for the reasons.
Get your P20EE fault checked
Send us the registration and the figure on any countdown, and we'll come to the vehicle and read the AdBlue system properly. If P2BAD is stored too, mention it.
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Eccles, Manchester M30 0SF