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Did Forced Regeneration Damage This DPF?
Imagine taking your vehicle to a mechanic, hearing them say, "We fixed it," only for the same issue to pop up minutes after leaving. This is exactly what happened to the owner of a Renault Trafic, leading to a frustrating cycle of unresolved errors, incorrect fixes, and one very unhappy van. Let’s unpack what was going on with this van, and why forced regenerations often do more harm than good.
The Symptoms
The Renault Trafic, with its updated 2.0L engine, wasn’t in a happy place. The dashboard was lighting up like a Christmas tree:
* Engine Failure Hazard Message
* Check Injection System
* Check Anti-Pollution System
* Stop/Start Error
Adding to these, both the spanner light and engine management light were staying firmly lit, pointing to deeper issues. But that’s just the start of the story. Despite visits to five different garages and attempts at forced regenerations, the problems kept returning.
Why The DPF Isn’t Always to Blame
A blocked Diesel Particulate Filter (DPF) got the finger pointed at it – as usual. Many consider the DPF a nightmare, but here’s the truth: it’s almost never the actual problem. The DPF works like a messenger, alerting you something else is wrong with the vehicle.
Here’s a relatable analogy: say you’ve got a flat tyre. A shop inflates it, sending you on your way. But a short drive later, it’s flat again. Pumping air into the tyre won’t solve the puncture – and pressing “regenerate” on a computer doesn’t magically fix engine faults. Yet, that’s what often happens with DPF complaints. A forced regeneration burns off soot temporarily, but if the real problem isn’t addressed, the issue will return.
Diagnosing the Issue
Using a ThinkScan 689 BT diagnostic tool, the external temperature sensor came up as a fault, along with errors linked to the DPF and engine oil dilution. While the oil level sensor fault was likely harmless, alarm bells were ringing for the DPF’s pressure levels.
Normally, a healthy DPF has a pressure reading between 2-6 mbar. This van? It had over 100 mbar at idle and shot up to 400 mbar at higher RPMs – clear signs of a severely blocked DPF.
External Temperature Sensor: A Key Player
The external temperature sensor played a surprising part here. The customer had replaced the wing mirror – which houses the temperature sensor – with a cheaper eBay model. The replacement wasn’t delivering accurate readings, causing the sensor fault to persist.
When the customer confessed to swapping the wing mirror back and forth, it became clear the fault code hadn’t been properly cleared after refitting the genuine mirror. With that reset, the sensor issue cleared up, leaving two main culprits: oil dilution and the blocked DPF.
Oil Dilution and DPF Damage
Oil dilution happens when excess diesel gets into the oil, often due to repeated regenerations. In this case, the DPF wasn’t reducing pressure despite multiple forced regens. This pointed to a damaged or melted DPF, likely caused by previous improper regenerations.
Damaged DPFs don’t just block; they trap unburnable material like ash or crystallised AdBlue residue. A forced regen, which burns soot, won’t clear this buildup. No amount of high-temp burning can fix a fundamentally damaged DPF.
Cleaning the DPF: A Test Run
The next step was a deep clean using a DPF cleaning fluid and compressed air. This process aims to flush out any non-combustible material clogging the filter. After cleaning, the pressure dropped significantly to around 14 mbar.
However, during a test drive, the pressure inconsistently spiked again during regenerations, confirming the DPF was physically damaged. Damage of this kind often means the expensive option: replacing the DPF entirely.
Why Forced Regens Are Risky
The van’s history showed numerous improper forced regens. When a DPF is packed with soot, forcing a regen without clearing other faults puts immense strain on the filter. This heats it beyond its limits, potentially burning or melting its structure.
This case highlighted how easily a poorly handled regen damages a DPF, leaving the owner to bear the costly consequences.
Conclusion
The real villain in this story? Rushed repairs and incomplete diagnoses. Most garages focused solely on clearing errors and running forced regens, ignoring why the DPF was clogging.
Ultimately, the DPF was severely damaged, likely from improper regenerations early on. For many, the only real solution will either be a DPF replacement or removal (depending on your preference and legality in your area).
This case reinforces a crucial point: a DPF warning is a symptom, not the disease. Fix the root issue early, and you’ll save yourself a lot of money and frustration in the long run. Always ask questions, push for a thorough diagnosis, and avoid shortcuts that only kick the problem down the road.