Peugeot P20EE Fault Code Fix SCR/NOx
P20EE on a Peugeot means the SCR system is not reducing NOx properly.
We diagnose the cause and get you back to a clean start, with mobile help across Stoke-on-Trent and Staffordshire.
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P20EE on Peugeot: SCR efficiency vs AdBlue tank failure
P20EE faults on Peugeot and Citroën vehicles are often misunderstood. Although the code refers to SCR efficiency, many drivers are told the AdBlue tank or pump module has failed. These are two different problems and diagnosing them correctly can prevent expensive parts being replaced unnecessarily.
| Problem | Typical symptoms | Common fix |
|---|---|---|
| SCR efficiency fault | P20EE returns after driving, NOx sensor readings abnormal | Sensor testing, injector inspection, exhaust leak check |
| AdBlue tank failure | Pressure faults, pump errors, warning appears soon after start | Tank or pump module repair |
If your vehicle shows symptoms related to the tank or pressure system, see the dedicated guide below.
Peugeot AdBlue tank fault guide
- Do not keep clearing the code and hoping it sticks.
- Check AdBlue level is genuinely above minimum (not “just topped up”).
- Do a short drive if safe, then re-scan and save the freeze-frame data.
- If the countdown is active, follow this step-by-step guide: No start in 500 miles.
Repeat SCR warnings don’t always mean the same repair. See DPF vs AdBlue warning to confirm what’s really triggering it.
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Use these links if you want the booking route, the main fix route, or repair detail.
What is P20EE on a Peugeot?
P20EE is “SCR NOx catalyst efficiency below threshold”. In plain English, your Peugeot thinks the exhaust is not being cleaned enough, even though the system is trying.
Most common vehicles we see P20EE on
- Peugeot Boxer
- Peugeot Partner
- Peugeot Expert
- Peugeot 3008
- Peugeot 5008
- Peugeot 308
- Peugeot 508
You can also see this on other PSA vans and cars with the same SCR setup.
Symptoms you’ll notice
- AdBlue warning and engine light.
- “Emissions fault” message.
- Countdown like “no start in 700 miles”.
- Limp mode on some models.
- P20EE keeps returning after you clear it.
Why P20EE happens on Peugeots
This code is rarely “just low AdBlue”. It is usually one of these:
- NOx sensor readings that do not make sense (sensor drift or failure).
- AdBlue dosing issue (injector blocked, crystallised tip, poor spray pattern).
- AdBlue pressure problem (pump weak, filter blocked, line restriction) — this is one of the most common issues we fix during an AdBlue repair.
- Exhaust leak before the SCR catalyst (false efficiency reading).
- SCR catalyst contaminated or worn.
- Software strategy that needs an update on some ECUs.
How we confirm the real cause
We do not guess parts. Every fault is confirmed with live data before we recommend an AdBlue repair or alternative fix.
- Full scan and freeze-frame review.
- Live data check for upstream and downstream NOx sensors.
- AdBlue pressure and dosing checks where supported.
- Road test when needed to see what triggers the fault.
Fix options we offer on site
- Targeted repair where the data points to a part or wiring issue — handled through our mobile AdBlue repair service.
- System clean-out if crystallisation and restriction show up.
- Calibration checks if the ECU strategy looks off for the readings.
- Software solution when repair costs do not stack up for you.
If you’re searching for AdBlue removal Stoke on Trent, we cover mobile AdBlue and SCR software work with no cutting or drilling.
Get it sorted without a garage visit
Send the fault code, your model, and whether a countdown has started. We’ll tell you the next step.
Stop the two pages competing
You might also want the “fast mobile fix” version of this guide.
Read the fast mobile fix path here.
That page focuses on the quickest route when you need the vehicle moving again.
Useful related pages
Peugeot P20EE FAQs
It means the SCR system thinks NOx is not being reduced enough. The ECU flags “efficiency below threshold” and may start a countdown.
Sometimes the warning message changes, but the code usually returns if the cause is dosing, pressure, sensors, or the catalyst.
Because the ECU still sees poor NOx conversion. A refill does not fix a blocked injector, weak pump, exhaust leak, or bad NOx readings — these need proper diagnosis and AdBlue repair.
Yes. On many Peugeot models it can trigger “no start in X miles” and start prevention once the countdown ends.
Why SCR faults get flagged so quickly
Modern diesels rely on SCR to cut NOx output. When the system readings do not line up, the ECU protects emissions control by logging efficiency faults like P20EE.
If you want background on emissions tech and testing, see DVSA’s Vehicle Market Surveillance Unit results for the 2024 emissions programme: DVSA 2024 emissions programme report.