Suspension sinks on Sundays! C5 X7 that works hard + 206 GTi HDi (and 406 Coupe and 306 HDi). - MattBLancs

[Huskyxantia]

Mine went 2 days with no risk warning popping up until 6 pm drive home .... up it popped on the dash by time i got home i was too knackered to mess around with the diagnostic, but today at some point I will see what the live data pulls up

[Huskyxantia]

So ive checked my ai notes and this is what was being recorded when my risk warnings were popping up on the dash display
The live Autel diagnostic logs from your work on the 308cc recorded the relative differential pressure values across the DPF as follows:
​Before Cleaning & Extended Road Test (High Soot / Pre-Regen): The differential pressure across the upper and lower pipes was hovering at elevated levels under load (often reading around 30\text{ mbar} to 50+\text{ mbar} at higher RPMs), which triggered the initial DPF warning light 8 miles into your drive.
​After Active DPF Regeneration (Post 52-Mile Test Run): Once the ECU completed the full burn-off cycle, the differential pressure dropped back down to baseline idle/low-load parameters (typically 0\text{ mbar} to 4\text{ mbar} at idle, and well under 15\text{ mbar} under load).
​This drop in relative pressure between the upper (inlet) and lower (outlet) pipes confirms that the exhaust flow restriction has cleared and soot mass is back to normal.

[Huskyxantia]

Then I gave it a question to a possibility that the heatwaves may of played a part in this .
Is it possible that 40° temperature this summer may of triggered lots of false risk of particular filter blocking warnings?

Ai said

Yes, extreme heatwave temperatures (like 40^\circ\text{C}) absolutely can trigger false or premature "Risk of Particle Filter Blocking" warnings on modern Peugeot HDi engines.
​Ambient Air Density & Oxygen Content
At 40^\circ\text{C}, the air entering the engine is significantly less dense and carries lower mass-oxygen per cubic meter. Even though the engine's MAP/MAF sensors account for air temperature, hot intake air leads to slightly less efficient combustion, which increases raw soot production in the cylinder before it even hits the DPF.
​Differential Pressure Sensor Voltage Drift
The DPF differential pressure sensor sits in the engine bay and measures the tiny pressure difference between the upper and lower pipes of the filter. At extreme ambient temperatures, the silicone diaphragm inside the pressure sensor can experience thermal expansion, and the internal piezoresistive circuit can drift slightly in voltage. This can trick the ECU into calculating a higher relative soot load than is actually present.
​ECU Passive Regeneration Interruption
Normally, a diesel car does a lot of "passive regeneration" while cruising on the motorway simply from hot exhaust gas burning off soot naturally. However, when ambient temperatures hit 40^\circ\text{C}, engine oil temperatures, coolant temperatures, and intake temperatures rise significantly. To protect the turbo and head gasket from overheating, the ECU will deliberately limit or delay triggering an active regeneration (which dumps extra fuel into the exhaust to raise DPF temps to 600^\circ\text{C}+).
​Because the ECU holds back on burning off the soot to protect the engine from melting in 40^\circ\text{C} heat, the calculated soot mass builds up past the threshold, popping up the "Risk of Particle Filter Blocking" warning on the dash.
​Once the ambient temperatures drop and the engine gets a steady run in cooler conditions—just like your 52-mile run—the ECU finally feels safe to run the burn-off cycle, the pressure normalizes, and the light turns off naturally.