Catalytic converter problem but car passes NCT

Muahahaha

Is the catalytic converter not part of the NCT under emissions? My engine light is orange and the diagnostic reading returned a code relating to the catalytic converter. Mechanic said he thought the NCT wouldnt even do an emissions test with the engine light on and it would fail on that basis. But I put it in anyway to see if anything else was going to fail it and it passed, any ideas why or how? Might it mean the CC is fine but its the engine light that is wrong to be lighting up?

BlakeS94

I thought that if there's an engine light they won't even test it, I suppose the NCT centres around the country are all inconsistent with each other.

I wouldn't go looking for trouble, if it passed, move on with your life for the next year or 2 and go back and deal with it then.

I find you can have a very different experience depending on the tester too, I've had lads who were genuinely sound and talked to me for a bit if it failed and likewise lads that just jump out of the car, grunt and gone back inside before you get a chance to say anything

mk7r

https://www.boards.ie/discussion/comment/118917154#Comment_118917154

A diesel is a fail with engine light on, petrol is a pass. OP you likely have a code for the rear 02 sensor or else the catalyst efficiency is below threshold. Neither of these will necessarily make the car fail the nct once the CO emissions are still in range.

teediddlyeye

I'm guessing your car is petrol OP? Also guessing you're getting P0430?

Does it have an aftermarket cat fitted? If so it may work fine but not be within the ECU tolerance. So you get an efficiency fault.

Used one of these on a mk4 golf a few years ago. Did the trick. Fit it to the o2 sensor after the cat.

O2 Sensor Adapter,2Pcs Oxygen Sensor Spacer Extender O2 Sensor Bung Extender Isolator for Exhaust Systems with M18 x 1.5 Sensor Holes https://www.amazon.co.uk/dp/B094QMKJ4X/ref=cm_sw_r_apan_i_2R6KY45CR84K8GXVCSHX?_encoding=UTF8&psc=1

Muahahaha

Yeah the car is petrol, was just surprised it passed given the engine light but all good. I need to get the problem fixed regardless but at least it didn't hold the NCT up.