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MOT emissions fail


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Hi  :)


I bought my 1st Scooby in Sept 2015. It has a full decat exhaust system which unfortunately failed MOT emissions test!

The engine management light came on the day before MOT so thought I would put through MOT anyway & see what came up.

Emissions reading were as follows


Fast Idle Test

CO: 0.563 Fail

HC: 51 Pass

Lambda: 0.999 Pass


Second Fast Idle Test

CO: 0.672 Fail

HC: 44 Pass

Lambda: 0.992 Pass


Natural Idle Test

CO: 0.650 Fail


I had a scanner on to see the fault codes. 2 codes P1410 & P2433.

This suggested the secondary air intake pump & was advised from my local garage to take to Subaru specialist. 

Booked into Subaru for diagnostic (£85) WOW!!! EXPENSIVE!!  :huh:

They also suggested same fault. They stripped it down and found out that it was fine. They suggested replacing a relay which they have now done. Checked emissions test again & said it was still high. Also mentioned that having no cat was going to make a big difference & probably won't pass an MOT without one.

They have suggested having a pre-cat fitted at turbo end . The question that I would like answered is: is all my emissions trouble going to be resolved by having a pre-cat fitted & will it pass MOT after? It is obviously going to be an expensive job & I'm worried that I will spend a lot of money to not resolve the problem. With my Scooby at Subaru it is costing me a small fortune!! Up to £300 already & nothing fixed!! 


Any help/advice will be appreciated. Thank You  

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The best and cheapest way is to ask around and see if you can get someone to *accidentally*(cough :rolleyes: ) ignore the CO on the emissions test. If you've brought the car with it already having been decat the chances are likely that it has been remapped. If this is the case, it may run really bad with the cat fitted or not at all so you would need to get it remapped again. 


Personally I know someone that can put it through for me and I'm sure if you ask the good people of SOC nicely they may be able to recommend someone in or around your area. Failing that I think you will be paying a lot of money.


You might also get lucky and be able to run a cat on the car at idle. If you do that you will just need to buy a cat (second hand I would advise) and cost for fitting and taking back off.

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You have to get inside the circle of testers. A strange and secretive club. A lot of us know one and no doubt there are many local to you. Expect to pay a little more for the mot. One option to find out is to phone local garages and ask for an mot, then mention the decat and ask "is there anything we can do about the emissions" subtle hints skating around the idea helps too [emoji5]

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Yeah I'll second what Ghost has said.

The smaller garages that are grateful for the work will not turn you away. Maybe if you let them do an oil and filter change to sweeten the deal that may help.

That does help. Return custom is always needed. I've used my mechanic pushing on 10yrs and quite a few different cars. I know to never trust a sale based on "fresh 12 month mot" [emoji12]
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I was told my scooby had a cat back exhaust on it when I purchased it only to find out come the mot a year later it was decatted. My emissions were similar to yours but luckily enough I know a guy that can still get an mot minus the emissions part so good luck on your search for a "friendly " tester. Best ask a tester at a small garage not a dealership or franchise like Kwik fit or Halfords.

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Thanks to all that replied  :)


Looks like I'm on the search for a friendly MOT tester lol

The only problem is the fault is still going to be there as engine management light is flickering on & off. Waiting on a call from Subaru today to give me my option's  :(

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Have a word with severn valley motorsport they are down your way and deal in mainly high powered gtr's etc but if you go down and speak to someone in person they may be able to advise you on the best way of sorting your problem out without main dealer prices etc

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