In brief — The FAP likes the temperature and regular journeys. When the DPF light comes on, the forced regeneration can save the day... provided you follow the procedure and check a few points afterwards. Okay, let's see about it together.
- When to intervene : light on, degraded mode, codes P24A4 Or P1435, regenerations too frequent.
- How to do it : on the road at ~3,000 rpm for 15–20 min, or launch static via OBD2 suitcase (20–40 min).
- Avoid breakage : monitor oil level, coolant, differential pressure sensor, EGR valve.
- Key thresholds : active regeneration around ~18 g, DPF indicator light around ~24 g, computer lock around ~40 g, probable replacement beyond ~45 g.
- When the workshop is necessary : regenerations which fail, saturated FAP, damaged monolith, HS sensors.
- Prevention : regular hot journeys, maintenance Eolys on FAP PSA additive, quality fuel, periodic diagnosis.
Forced DPF regeneration: warning signs and good timing
When the DPF light lights up and the car shifts to degraded mode, there forced regeneration becomes a serious option. The computer usually launches an active regeneration around ~18 g of soot. Towards ~24 g, the alert is displayed because the cycle was not successful. From ~40 g, the calculator blocks any attempt to protect the monolith.
Typical symptoms before the procedure
Loss of power, fan remaining active after shutdown, increased consumption, slightly high idle speed. The P24A4 fault code often appears on *Peugeot*, *Citroën*, Ford engine or *Fiat*. On *Renault*, a P1435 may appear. Frankly, there are worse things, but it's better to act quickly.
Concrete example to situate the emergency
Case of a *Peugeot 308 HDi* driving mainly in town: interrupted cycles, soot estimated at 23–24 g, warning light on. A straightforward drive at 3,000 rpm on the ring road was enough. Conversely, a *Citroën Berlingo* utility vehicle arrived in the workshop at ~40 g and required external cleaning. This is what experience recommends: act before the critical level.
Safe procedure for forced DPF regeneration, on the road or when stationary
Don’t panic, it’s simpler than it seems. Two options exist: dynamic cleaning on the road, or regeneration static via OBD2. The idea remains the same: reach 550–650°C in the exhaust to burn the soot without damaging the filter.
On the road, simple and effective method
- Raise the engine to ~3,000 rpm in 3rd/4th for 15–20 min on a clear expressway.
- Cut off large consumers (manual air conditioning if necessary), engine at normal temperature.
- Monitor the absence of jerks and keep a stable regime. If the DPF light goes out, the cycle is successful.
A little mechanic’s advice: avoid jerky journeys. A steady pace helps the calculator maintain the target heat and completes combustion.
When stationary, via OBD2 case
A compatible case allows you to order the stationary cycle (20–40 min depending on model and soot mass). Provide workshop ventilation, a fit battery and never do this in a closed room. The computer cuts the EGR, controls the post-injection and stabilizes the speed to reach the temperature.
Avoiding breakage after regeneration: essential checks
Successful forced regeneration is not the end of the story. A few checks avoid collateral damage. First, controlling the oil level. A dilution can occur through post-injections. If the level rises or if the oil seems to smell like fuel, an oil change is necessary.
Monitor cooling and sensors
Look at the coolant and check for bubbles or recent overheating. Then look at the differential pressure sensor and its hoses. An inconsistent reading can restart cycles too often and fatigue the turbo, which affects turbo reliability. The clogged EGR valve also disrupts combustion and accelerates the clogging of the DPF.
When the lights persist
If the light remains on after regeneration, a stored fault may require resetting. A suitcase helps confirm the actual soot rate and the status of the probes (including the Lambda probe on certain blocks). If a code comes back immediately, it is better to diagnose before persisting.
Practical conclusion of this step: regenerate, then validate the FAP environment to avoid the yo-yo effect.
Forced regeneration, professional cleaning or replacement: what to choose?
It all depends on the soot rate, the history and the internal condition of the filter. Forced regeneration addresses a clogging of soot, not an overload of non-combustible ash. External cleaning squares a saturated but healthy filter. A replacement is considered when the monolith is cracked or out of tolerance.
| Solution | Triggering | Duration | Typical use | Risks if poorly done |
|---|---|---|---|---|
| Passive regeneration | Warm and regular journey | ~15–20 min | Periodic natural maintenance | Cycle interrupted, residual soot |
| Active regeneration | Computer to ~18 g | ~10–20 min | City + mixed road | Temporary overconsumption |
| Forced regeneration | Indicator light to ~24 g | Road or OBD2 | Clogging advanced reversible | Overheating if poorly monitored |
| Professional cleaning | Blockage around ~40 g | Varies | Soot + ashes to evacuate | Quality depends on the process |
| Replacement | > ~45 g / HS monolith | — | Last resort | High cost if late |
Example terrain: a fleet of *Citroën Berlingo* utility vehicles on short urban journeys often ends up in hydrodynamic cleaning when the cycles repeatedly fail. Better that than burning out a DPF from too much heat.
Prevent DPF clogging on a daily basis
The best economy is prevention. Organizing a sustained journey each week is often enough to keep the FAP clean. Aim for a section of fast track, stable revs and warm engine. Avoid switching off immediately after a regeneration in progress, otherwise you risk restarting later with a half-loaded filter.
Fuel, additives and PSA cases
Good quality fuel limits soot. On PSA models with additive FAP with Eolys (or cerine), the combustion threshold drops around 450°C and the cycle lasts a short time. The additive tank must be topped up periodically, usually around the major overhaul. Failure to do so results in ineffective regenerations.
Gasoline and GPF, same reflexes
Certain recent gasoline engines with GPF share the general logic: too short journeys equal coughing filter. The “regular hot journey” reflex remains valid, even if the symptoms are less marked than in diesel.
If you hear this noise, it is often a sign that the fan is forcing itself to cool down after a cycle: let the motor finish quietly. The takeaway here: Consistent driving and a few simple habits are better than a high-cost replacement.
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As soon as the DPF light comes on and sustained driving does not turn it off, or if a P24A4/P1435 code indicates a clog. Beyond approximately 24 g of soot, the procedure becomes relevant; beyond approximately 40 g, you must undergo professional cleaning.
Can we do a stationary regeneration at home?
Yes with a compatible OBD2 suitcase. Provide ventilation, battery in good condition and constant monitoring. Duration typically varies from 20 to 40 minutes depending on vehicle and soot load.
Why can oil rise after regeneration?
Due to post-injections, some fuel may pass into the oil. If the level rises or the smell is strong, drain and filter.
Can a tank additive replace regeneration?
No. It can help prevent clogging, but it does not replace the temperature rise needed to burn off the soot. On PSA additive FAP, Eolys lowers the combustion temperature but does not eliminate the need for cycles.
What should I do if the light stays on after a successful regeneration?
Check and reset the differential pressure sensor, check the actual soot mass with a suitcase, and ensure that no cycle has been interrupted. If the fault returns, direct the diagnosis towards EGR, sensors, leaks or turbo.