Audi A4 Exhaust System: Specs, Fitment & Common Faults
On the A4, power loss and heavy smoke that looks like DPF failure can genuinely be a faulty exhaust back pressure sensor giving incorrect readings — plus a legal clarification that DPF deletes aren't actually legal in the UK.
Illustration for editorial purposes
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Audi A4 Exhaust System: OEM Part Number
| Front pipe with catalytic converter (petrol) | Genuinely a different part from the diesel front pipe below — confirm your exact engine code before ordering, since petrol variants use several distinct references across the range |
|---|---|
| Front pipe with diesel particulate filter (diesel, where fitted) | A genuinely different assembly from the petrol cat pipe — combines the catalytic and particulate filtration function in one unit on most diesel engines, not sold as two separate parts |
| Centre/intermediate pipe | A genuinely separate section from both the front pipe and rear silencer, confirmed in VW Group's own workshop documentation as a distinct assembly |
| Rear silencer, front-wheel drive | VW Group's own workshop manuals confirm a genuinely different silencer and mounting arrangement for front-wheel-drive cars versus Quattro — the underbody routing differs enough that the two aren't interchangeable |
| Rear silencer, Quattro | A genuinely different silencer and mounting from the front-wheel-drive version above, to clear the rear differential and driveshaft routing |
| S4 rear silencer | A genuinely different, larger-bore system from the standard TFSI/TDI, and on some versions includes an active valve that changes the exhaust note by driving mode — not a like-for-like swap with the standard rear silencer |
Audi A4 Exhaust System: The Part That Announces Its Own Problems
On the Audi A4, sound is usually the first clue here, ahead of any visual sign — a rattle, a drone, noise that's crept in gradually or arrived overnight. It's one of the more forgiving faults in that sense, since your ears will likely flag it before it becomes a bigger problem.
Audi A4 Exhaust System: What It Does
The Audi A4's exhaust system handles three things at once: clearing burnt gases from the engine, cutting noise via the silencer, and treating emissions through a catalytic converter and particulate filter. Because petrol and diesel emissions requirements differ, it often uses genuinely different exhaust systems depending on engine type.
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A Genuinely Money-Saving, Real Finding Worth Knowing Before Assuming DPF Failure — Audi A4 Exhaust System
If you're facing power loss and heavy smoke alongside a warning light, this is genuinely worth knowing before assuming the DPF itself has failed: one documented case saw these exact symptoms traced to a faulty exhaust back pressure sensor, which was giving incorrect readings and causing incomplete DPF regeneration cycles. Replacing this specific sensor and cleaning the exhaust system resolved the fault entirely.
It's also genuinely worth knowing an important legal clarification: removing emissions control equipment fitted to achieve type approval is already a legal requirement not to do in the UK, and while a "DPF delete" might currently pass an MOT test, this doesn't make the practice itself legal — worth knowing this carries genuine legal risk regardless of current MOT outcomes.
Audi A4 Exhaust System: 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 Audi Exhaust System
The same part, covered across other Audi models.