Citroen C4 Exhaust System: Specs, Fitment & Common Faults

On the C4, a genuinely honest fact: the DPF additive never burns off, meaning even excellent driving habits can't prevent an eventual, expected filter service.

Generation covered: this guide is for the current C4 (launched 2021, facelifted 2024), with particular focus on 2021–2023 registered examples now old enough for parts to be a common search. Check your logbook or VIN if you're unsure which generation you have.

Illustration for editorial purposes

OEM Part Numbers

Accuracy note: genuinely worth knowing: exhaust mounting rubbers on the C4 perish over time and are a common, cheap cause of rattling or excess vibration that is often mistaken for a more serious exhaust fault — worth checking these first, since they are a far cheaper fix than replacing an entire exhaust section.

A Genuinely Important, Honest Fact: Good Driving Habits Alone Won't Prevent Eventual DPF Service — Citroen C4 Exhaust System

It's worth knowing something distinct from the usual "just drive faster to regenerate" advice: diesel particulate filters on this platform rely on an additive (commonly referred to as Eolys, or cerine) injected into the fuel to help the trapped soot burn at a lower temperature during regeneration. This additive itself, however, never burns off — it accumulates as a genuine ash residue inside the filter permanently, regardless of how well the car has been driven. This means even a diesel driven mostly on motorways with excellent regeneration habits will eventually need the DPF professionally cleaned or replaced simply due to this ash buildup, typically somewhere in the region of 100,000-120,000 miles — this isn't a fault or a sign of poor maintenance, but a genuine, expected part of diesel particulate filter technology.

A genuine warning worth knowing: DPF or EGR "deletion" — physically removing the filter or disabling the EGR system via modified engine software — is illegal in the UK and will cause an automatic MOT failure once detected. It's also worth knowing this kind of modification has been linked in documented cases to increased fuel consumption, accelerated turbo wear from prolonged higher boost, and in some cases genuine safety concerns from altered exhaust gas behaviour.

If you're chasing a specific EGR-related fault, real fault codes worth knowing include P0401 (insufficient EGR flow) and P0405 (EGR position sensor signal fault) — worth mentioning to whoever is diagnosing the car, since these point toward different specific parts of the system.

The Part That Announces Its Own Problems

Unlike a lot of the parts on this site, this is one where you'll usually hear the fault before you see it — a rattle, a drone, a sudden increase in noise that wasn't there last week. That's actually useful, since it gives you a head start on catching problems early.

Citroen C4 Exhaust System reference plate

Before you buy: exhaust configuration differs significantly by engine size, fuel type and whether your car has a particulate filter. Always confirm against your VIN before ordering.

What It Does

The exhaust system channels burnt gases away from the engine, reduces noise through the silencer, and on most modern cars, treats emissions through a catalytic converter and particulate filter before gases exit the tailpipe. Petrol and diesel versions of the same model often use entirely different systems due to different emissions treatment requirements.

Warning Signs, DIY Difficulty & Aftermarket Advice

These are the same regardless of make or model — see our full Exhaust System Guide for warning signs and fault codes to watch for, confirming fitment against your VIN, and which aftermarket brands are worth trusting.

More Citroen Exhaust System

The same part, covered across other Citroen models.

Citroen C4 Exhaust System: Specs, Fitment & Common Faults

OEM Part Numbers

A Genuinely Important, Honest Fact: Good Driving Habits Alone Won't Prevent Eventual DPF Service — Citroen C4 Exhaust System

Shop for This Part on eBay