Peugeot Boxer AdBlue Faults Explained: P20E9, U029D, and Fixes

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September 12, 2025

Why Peugeot Boxer Vans Suffer AdBlue Faults

Many Peugeot Boxer owners run into AdBlue system warnings, no-start countdowns, or sudden limp mode. These problems are common across Euro 6 vans and usually come from sensors, pumps, or clogged dosing systems. Two of the most frequent codes are P20E9 and U029D.

What Does Fault Code P20E9 Mean?

P20E9 relates to “Reductant Pressure Too Low.” In simple terms, the AdBlue pump cannot build enough pressure to inject fluid into the exhaust system. Common causes include:

  • A failing AdBlue pump or pressure sensor
  • Crystallised AdBlue blocking lines or filters
  • Electrical faults in the dosing system

Left untreated, this fault often triggers limp mode and an MOT emission fail.

What Does Fault Code U029D Mean?

U029D refers to “Lost Communication with NOx Sensor B.” This means the van’s ECU cannot read the rear NOx sensor, which monitors emissions after AdBlue injection. Typical reasons include:

  • Damaged wiring or connectors to the NOx sensor
  • Failed NOx sensor (very common on Boxers)
  • Software mismatch after battery or ECU work

Without a working NOx sensor, the ECU assumes high emissions and can trigger a no-start countdown.

Other Common Peugeot Boxer AdBlue Faults

  • AdBlue heater faults causing freezing in winter
  • Clogged injectors leading to poor dosing
  • Fault codes such as P20E8 and P2BA9 linked to fluid quality

How to Fix These AdBlue Issues

At Pro Remapping, we deal with Peugeot Boxer AdBlue faults daily. Depending on the diagnosis, we can:

  • Replace or reset faulty NOx sensors
  • Flush and reset the AdBlue system
  • Update ECU software to handle known glitches
  • Offer safe AdBlue removal options where legally permitted

Why a Professional Fix Matters

DIY resets may clear the light temporarily, but without addressing the root cause, the issue will return. Our team uses dealer-level tools to test pressure, dosing rates, and live NOx data. This ensures the right repair the first time.

Local Peugeot Boxer Solutions

If you own a Peugeot van and need a reliable repair, our Peugeot Boxer AdBlue fault page covers common issues and solutions. For wider fixes, see our AdBlue repair service.

Book Your Peugeot Boxer AdBlue Repair

Don’t let a P20E9 or U029D code take your van off the road. We cover Stoke-on-Trent, Staffordshire, the Moorlands, and Cheshire East. Call Abid on 07404 022260 or Najib on 07386 547990 to arrange a same-day fix.

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