Diagnose the system—not the dashboard
The warning is urgent.
The repair still needs proof.
Practical guidance for DPF, AdBlue, SCR, EGR, NOx-sensor and diesel-additive faults—built around the questions drivers and garages ask when the warning returns.
Choose the warning you recognise
Countdown?
Blocked again? Fault returned?
A forced regeneration, sensor or replacement part may be the correct answer—but only after the cause has been tested. Start with the situation closest to yours.
AdBlue countdown or no-start warning
An AdBlue countdown can continue after a top-up when the vehicle has detected a system fault. Diagnosis should identify the cause before parts, coding or adaptations are authorised.
DPF regeneration keeps failing
Repeated DPF regeneration failure may be caused by the filter, sensors, operating conditions or another engine fault. Test the reason before forcing the process again.
EGR fault returned after replacement
If an EGR fault returns after replacement, test actuator response, wiring, airflow and the wider system instead of ordering the same part again.
NOx sensor or wider AdBlue fault?
A NOx-sensor code can be caused by the sensor, its circuit or the wider emissions system. Compare the evidence before authorising an expensive replacement.
Peugeot/Citroën additive pump fault
Peugeot and Citroën diesel-additive faults need system diagnosis, not an automatic DPF replacement. Test the pump, circuit, fluid system and recorded data.
DPF pressure sensor or blocked filter?
DPF pressure data must be checked for plausibility before deciding whether the sensor, pipework, wiring or particulate filter is responsible.
A dashboard photograph can save the first round of guesswork.