Subaru Impreza Exhaust System: Specs, Fitment & Common Faults
On the Impreza, a catalytic converter on a related model was genuinely replaced multiple times under warranty, with the same code returning each time, because the root cause was never diagnosed.
Illustration for editorial purposes
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OEM Part Number: confirm via VIN — Rear silencer (aftermarket) Bosal 229-683
| Rear silencer (back box) — aftermarket | Bosal 229-683; Vegaz SAS-56, SAS-43IMA, SAS-44, SAS-55IMA, SAS-60, SZS-50 (880 mm), SAS-18; Polmo 46.20-46.23, 46.25 (AWD, "from 1999" mismatch); Izawit 45.006, 45.007 (660 mm) |
|---|---|
| Centre / intermediate silencer — aftermarket | no brand refs (engine links only: 1.6i GT2/GT3, 2.0i GT6/GT7, e-BOXER GTE) |
| Front pipe / catalytic converter (DPF on diesels) — aftermarket | or DPF: Bosal 090-640 (Euro 3); Walker 28249 (740 mm), 28747 (450 mm); Ernst 757997 (880 mm, Euro 3/4); BM Catalysts BM91070H, BM91976H, BM80563H; JMJ 1091581 (EJ20 family), 1090122, 1091686 |
| Genuine (OE) numbers quoted | None quoted in catalogue listings — order genuine parts against your VIN |
| Fitment notes | Petrol and hybrid only; same generic Subaru list as XV/Forester/Outback. |
Subaru Impreza Exhaust System: The Part That Announces Its Own Problems
On the Subaru Impreza, most faults are things you'd spot visually first, but this one usually announces itself acoustically — a rattle, a drone, a noticeable jump in noise levels. That's actually helpful, since it means you'll likely notice trouble well before it gets serious.
Subaru Impreza Exhaust System: What It Does
Three jobs happen inside the Subaru Impreza's exhaust system: routing burnt gases away from the engine, quieting them through the silencer, and treating emissions via a catalytic converter and particulate filter. Petrol and diesel variants often need completely different systems to meet their respective emissions requirements.
Subaru Impreza Exhaust System: Watch: Replacing It
Muffler delete on a 2017 car, not a like-for-like replacement
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A Genuinely Alarming, Honest Real Account Worth Knowing — Subaru Impreza Exhaust System
If you're facing a recurring P0420 code and catalytic converter replacement, this is genuinely worth knowing before agreeing to another straight swap: documented cases on related Subaru models describe the catalytic converter being replaced under warranty multiple times, with the exact same code returning each time, because the underlying root cause was never actually diagnosed — only the symptom repeatedly swapped out.
It's also genuinely worth knowing that P0420 doesn't automatically mean the catalytic converter itself has failed — the code relates to catalyst efficiency falling below an expected threshold, which can be triggered by several other causes without the converter being physically damaged at all.
Subaru Impreza 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 Subaru Exhaust System
The same part, covered across other Subaru models.