Citroen C5 Diesel Particulate Filter DPF

The DPF on a Citroën C5 diesel is a ceramic filter located on the exhaust line after the catalytic converter. It traps harmful soot particles emitted by the diesel engine, filtering down to 0.1 micron using a porous silicon carbide structure.

Citroën C5 diesel engines emit soot composed of carbon, hydrocarbons, sulfate, sulfur and metallic oxides that are harmful to health and the environment. The DPF captures these particles to reduce pollution and comply with European emission standards.

The DPF regeneration cleans trapped particles through two main modes :

• Passive regeneration: During driving conditions with exhaust gas temperatures around 550 to 600°C, usually on highways or open roads, soot burns naturally.
• Active regeneration: When conditions are insufficient, the engine injects extra fuel into the exhaust to raise DPF temperature to about 450°C aided by a special fuel additive (EOLYS 176), which lowers combustion temperature for soot.

This regeneration manages soot accumulation and prevents clogging.

The Citroën C5 uses a dosing system adding an additive fluid called EOLYS 176 to the fuel. This additive reduces the temperature needed to burn soot in the DPF from 550°C down to 450°C, making regeneration more efficient and lowering emissions.

• Regularly refilling the additive tank is required for proper DPF function.
• Failure to maintain additive levels may cause warning messages and reduced engine performance.

This system is specific to PSA group vehicles (Citroën and Peugeot).

The engine ECU monitors soot load using pressure sensors placed before and after the DPF. It triggers different regeneration levels depending on the soot amount :

• Level 1: Heating the catalytic converter to operational temperature.
• Anticipated regeneration: ECU activates regeneration early if driving conditions allow efficient cleaning.
• Forced regeneration: Complete cleaning by holding engine at high RPM with post-injection to burn soot fully.

These automated steps help maintain filter efficiency and engine performance.

Over time, combustion of soot particles leaves behind ash which accumulates in the DPF. Excessive ash causes filter clogging leading to :

• Increased exhaust back pressure
• Engine power limitation (for example, max 2200 RPM)
• Warning lights or messages on the dashboard

Regular maintenance and cleaning are essential to prevent severe clogging and costly replacements.

DPF maintenance typically involves :

• Performing a forced regeneration using a diagnostic tool that raises exhaust temperature and clears soot.
• Cleaning or replacing the DPF when ash buildup is excessive.
• Refilling the additive tank for EOLYS fluid as required.
• Resetting the ECU fault codes and system status after maintenance.

Some DIY enthusiasts can remove and manually clean the DPF using basic tools, but care is required.

A new DPF does not require a regeneration before installation as it starts clean. After fitting a new filter, the vehicle's ECU must be reset to recognise the new part and the system should be tested to ensure correct pressure sensor readings and regeneration cycles.

• It is important to check additive levels and refuel the tank if necessary.
• Drive the vehicle under conditions allowing passive regeneration (steady highway driving) to help condition and activate the DPF system properly.

Following correct installation and reset procedures ensures optimal DPF performance and longevity.