Citroën Relay DPF Removal Cleaning: Fixing a High-Mileage Recovery Truck

This Citroën Relay serves as a reliable recovery truck, but high mileage often spells trouble for the DPF. The DVSA inspectors spotted the issue during a roadside check. They towed it to a garage, lifted it on a pit, and inspected the exhaust system closely. 183,000 miles: A clear sign of wear, as the DPF has endured years of stop-start driving. Seven-day deadline: The truck needed urgent DPF repairs to pass compliance. The engine management light stayed on, hinting at deeper problems beyond a simple reset. Why the Warning Lights Came Back On The owner had the DPF cleaned at another garage just days earlier. Mechanics there claimed it was spotless, yet the lights returned almost immediately. Lights back on. Reading the Fault Codes We hooked up the Launch X431 Euro scan tool to pull the codes. This device gives a full picture of the engine's health. Buy Launch X431 Euro here... www.launchtech.co.uk Key Codes Explained 1. P242F: The DPF has exceeded its limits, often from ash overload. 2. P15 additive: Signals a problem with the additive tank level or function. 3. Particle filter warning: Direct alert for DPF restriction. 4. Inlet air circuit fault: Possible leak or pressure issue in the intake. These codes scream blocked and worn DPF, with the additive system ignored in prior fixes. Analyzing Live Data Streams Live data from the scanner painted a stark picture. We focused on exhaust information streams to spot patterns. Exhaust Information Insights Regens happened every 159 kilometres, far too frequent for a healthy system. Normal intervals stretch much longer. DPF pressure sat at 27 millibars, well above the ideal 2-6 range. Additive deposited totalled 89 grams, a red flag. This excess leads to irreversible ash buildup. Why This Points to a Worn DPF Soot burns off during regeneration, but ash from the additive does not. It clogs the filter over time, especially in high-mileage vans. Town driving worsens it, as the DPF rarely hits 600°C to self-clean. Back-flushing off the vehicle became our only option. Understanding the Additive Tank Confusion Many mechanics mix up the tanks on these vans. The additive tank isn't the AdBlue one. It's a separate diesel additive system, often called Eolys or Pat fluid. AdBlue tank: Handles NOx emissions by injecting into the exhaust. Additive tank: Mixes with fuel to lower regen temperatures. We found this tank bone dry. How the Additive Works in DPF Regeneration Performing the Smoke Leak Test To rule out intake issues, we ran a smoke test with the Launch Smoke 2 machine. It pumps pressurised smoke into the system for easy leak spotting. Results and Next Steps No leaks appeared after several minutes. The inlet fault likely stemmed from DPF backpressure. Other culprits include a stuck EGR valve, vacuum leaks, or faulty turbo. Cleaning the DPF often clears this code. Removing the DPF and Additive Tank Brian handled the disassembly with care. We disconnected the turbo clamp, and rear silencer clamp. The additive tank next after unbolting and removing the fuel line. It was empty. The Off-Car DPF Cleaning Process We used the Carbon Clean DCS 16 machine for a thorough off-car clean. This setup blasts water and air to flush deep blockages. this is available from www.carbon-clean.co.uk AdBlue and NOx sensors stayed in place to seal holes. We bridged pressure pipes with tubing and filled the tank with water. Flushing Out the Ash Blasts started at 2 bar, ramping to 4 bar. Red ash poured out immediately, mixed with oil. This was the worst we'd seen, over 20 flushes of pink water and crystallised additive from the injector port. First flush: Heavy red ash floods the bucket. Mid flushes: Oil traces and persistent red tint. Later flushes: Water runs almost clear. On-car cleans miss this ash entirely. Euro 6 vans like these Citroëns and Peugeots build ash fast after 80,000 miles, unlike Euro 5 models that hold up to 250,000 on simpler jobs. Reinstalling and Resetting the System Everything slotted back neatly. We refilled the additive tank with fresh Eolys fluid. Clearing Codes and Special Functions 1. Run "spare part emissions particle filter" to reset as cleaned. 2. Let the engine idle for one minute, then switch ignition off for 30 seconds. 3. Perform "draining and filling of URA reservoir" for the additive tank. Live data showed 2,600 units, confirming a full tank. Final Checks and Pressure Test We revved to 3,000 RPM for minutes. Pressure dropped from 20 millibars to 3 as the wet DPF dried. No codes returned, and lights vanished. Successful Outcome and Customer Relief The truck passed with flying colours. Initial high pressure worried us, but the clean worked wonders. The owner gets his recovery van back, compliant and reliable. If your Citroën or Peugeot van shows DPF lights, don't delay a proper clean. Have you faced similar issues? Share in the comments, and watch for more fixes from O'Rileys Autos.