2007 Outback 2.5 Cat Failure

[Seb_]

Hi All,

I've had engine warning light come on and my Cruise light flash repeatedly.

I checked my ODB2 finding  P0420 - Powertrain - Catalyst System Efficiency Below Threshold (Bank 1) fault.

My local garage advised that this could be the lamda sensor failing rather than the cat, so I replaced that and cleared the fault code.

Subsequently I've had the engine warning light come back on, and the fault code return, so having spoken to my garage again they've advised the cat needs to be replaced.

What are my options here?  The car has sone 105k miles and I'd like to get another 100k out of it, it's in very good order generally.

I don't want to fit a cheap aftermarket cat, if I replace it I'll use an OEM or premium aftermarket option, which doing some research is going to cost me around £500-£600.

The garage has suggested I de-cat the car until the MOT, then see if it fails due to emissions, and if it does replace the cat at that point.

I guess my questions are:

1. Has anyone here de-cat'd their Outback 2.5 and had it pass an MOT?
2. Is there a way to permanently clear the fault code that will be caused by the decat?

I'm happy to spend the money on a cat if I need to, but I'd prefer to spend it on a tow bar and lift kit. 😂

Any advice much appreciated.

[Jay762]

I have 2.5l decatted imprezas and they pass MOT no problem. I do try and keep it all combusting right - good plugs and fuel etc but no issues so far

[Mr B]

Seems your garage doing lot of guessing as don't know how to test .
Thing that concerns me is cat failure at that low mileage .
Did they not do live data on lambda readings and thermal temp scan of cats get idea what likely wrong !?
If they replaced Lambda sensor what was fitted ? oem or aftermarket. These cars are super fussy on Lambda and oem denso what best used, anything else results in more faults .
Hopefully they kept the original sensor .
Generally speaking you can tell sensors working and cat health to some extent from pre and post Lambda readings and reaction, thermal readings of cat helps determine if it working .
Seems low mileage for cat failure and makes me wonder if underlying issue of fuelling or burning bit of oil .

Technically removing cat is illegal, can get your car confiscated and you in court . Emission equipment checks more stringent and only getting more so, it harder for garages be lenient on these areas, is an option though .

Seems no real diagnosis been done I be reluctant throw silly money at oem or aftermarket cat as it might not be the problem and an underlying issue could ruin new part bringing you back to square one .

I would consider second opinion from someone who can test it bit further and consider used oem cat or cheaper aftermarket cat like BM and buy it at low price, can get on eBay via carpartsinmotion with 15 to 20% off as they often in eBay coupon promotions
https://www.ebay.co.uk/itm/Catalytic-Converter-Type-Approved-BM91425H-BM-Cats-44105AG100-44620AA401-Quality/333846221297

Personally I like oem but new oem with all required parts is stupid money (parts and fitting can exceed car value), sensible priced used can be effective route. We done a couple with BM as some customers simply want cost viable and they not too bad .
Also if your EML warning light not coming on quickly after reset you more likely pass MOT as is and codes cleared right before test .

I would take your time make wise choice on solution selection and try find a garage that can be more conclusive in diagnosis .