Peugeot Boxer, Citroën Relay and the Ford-badged Transit Custom share the same PSA SCR hardware from 2019 onward.
When that hardware hiccups, the dashboard spits out a mix of “P-codes” that look similar but flag very different faults.
Scroll through the top ten AdBlue trouble codes logged in PSA–Ford’s 2024 joint bulletin , see what each one really means, and learn the fastest roadside checks before you order pumps, heaters or sensors.
Bookmark this list next to the Mercedes code library and you can diagnose 90 % of SCR calls in five minutes, saving tows and wrong-part returns.
If a code won’t clear after the basics, book a same-day flash via the mobile AdBlue hub in Stoke.
Top ten Boxer / Relay / Custom AdBlue codes
| Rank | Code | PSA description | Quick clue |
|---|---|---|---|
| 1 | P20E8 | Reductant pressure too low | Silent pump prime; filter gauze clogged |
| 2 | P20EE | SCR efficiency below threshold | Both NOx sensors > 300 ppm at 2 000 rpm |
| 3 | P13DF | Heating element open circuit | Heater current 0 A, fuse 31 blown |
| 4 | P204F | Reductant system performance | Mixed bag; often P20E8 + P20E9 history |
| 5 | P20E9 | Reductant pressure too high | Return hose kinked behind tank strap |
| 6 | P207F | Reductant quality low | Urea concentration reads < 31 % |
| 7 | P229F | Post-cat NOx sensor slow | Heater current < 3 A, connector corroded |
| 8 | P2BAE | NOx exceeded — torque limited | Usually piggybacks P229F after 3 cycles |
| 9 | P2BAF | NOx exceeded — speed limited | Starter lock starts 500 km later |
| 10 | P2BAC | SCR catalyst deterioration | High mileage; catalyst faces white and brittle |
Code triage in five minutes
Key on, engine off, scroll live data.
If pump pressure sits below 3 bar or above 9 bar at priming, jump straight to the filter or return hose before touching sensors.
Pressure normal yet NOx hits 400 ppm at idle? Swap the downstream sensor or flash the SCR map—heater drift fools the ECU into overdosing.
Quality codes like P207F rarely mean fluid “gone off”; eight times out of ten someone has topped up from a drum left open to rainwater.
Drain two litres into a clear jug; brown swirl equals diesel splash, chalky streaks equal crystal slurry.
For P13DF heater faults, check fuse 31, then heater current; if it draws zero amps the element is dead even if the fluid hasn’t frozen.
Mobile fix options
A service van can:
- Swap a clogged tank filter and flush lines in 25 min.
- Code new NOx sensors with Autotuner bench mode.
- Flash the latest PSA SCR map that widens pressure thresholds.
- Install a heater bypass resistor for export or off-road only vans.
Code won’t clear?
Ring 07503 134 362 and get a pressure/no-start countdown check on site.
Frequently asked questions
Can I clear P20E8 by topping up AdBlue?
No—low pressure is mechanical; topping up doesn’t boost pump pressure.
Will a sensor delete clear P207F?
Deleting NOx sensors clears the code but makes the van illegal on UK roads.
Does crystal buildup always need a tank swap?
No. A warm flush and new filter cures most Boxer/Relay tanks.
