Amber engine light on. Will car pass nct?

spacekiwi

I see this is a issue on here alot...however posts seem a few years old and just wanted to know story now..
Will it fail if light on? Will they not test emissions if light on?? Thanks

biko

If petrol - yes
If diesel - no

Atlantic Dawn

If you have a fault reader you could clear the code but it's likely it will appear again, possibly after a short drive depending on what is causing it. If you disconnect the battery for about 2 mins and reconnect that will also clear it but if you have a radio requiring a code you will be asked for a code when you reconnect.

Rkskandrius

It will not fail on engine man. light being on. However, the light is on for a reason, it might fail emission test.

jimbis

I always thought it was a fail if the engine management light was on. Nice to hear that's no true.

Leonard Hofstadter

jimbis wrote: »

I always thought it was a fail if the engine management light was on. Nice to hear that's no true.

Only for petrols is the EML on not an NCT failure - but that very much depends on the cause of the EML being on.

If the EML is on because of a fault in some part of the car's emissions control system, then it will fail the NCT because the emissions will be too high. Common faults on many petrols are coil packs and MAF (air flow meter) failures - the former will cause a lot of unburnt fuel to be sent into the exhaust and thus the catalytic converter so if not attended to promptly will result in a very expensive repair bill not to mention making the car fail on hydrocarbon emissions, while the latter will cause the lambda (air/fuel ratio) to move away from the ideal value of 1, which can also result in catalytic converter failure, increased fuel consumption and possibly internal engine damage (if the AFR goes above 1 for a sustained period of time, as running lean is definitely not good for an engine unless it's a direct injection unit - these are designed to run lean under low engine loads).

So OP, just because the light being on doesn't necessarily mean you'll fail the NCT (assuming it's petrol), it does not for a second mean you should ignore it. The light is on for a reason and there is something wrong with some part of the engine's electronics, so it needs to be looked at as soon as possible.

biko

dr.fuzzenstein

The attitude to warning lights and error messages in modern cars never fails to baffle me. The opinion seems to be they are just an annoyance that pops up for no reason other than to cause an inconvenience and they have to be reset or ignored.
The reason there is a warning light is because something isn't right, so the correct remedy is not to just make the light go away, but to find the problem and fix it.
OP, what car and what light? Do you get an error message?

Special Circumstances

dr.fuzzenstein wrote: »

OP, what car and what light? Do you get an error message?

I'm willing to bet on the country of the brand, and the brand family of the car ;-)

CiniO

dr.fuzzenstein wrote: »

The attitude to warning lights and error messages in modern cars never fails to baffle me. The opinion seems to be they are just an annoyance that pops up for no reason other than to cause an inconvenience and they have to be reset or ignored.
The reason there is a warning light is because something isn't right, so the correct remedy is not to just make the light go away, but to find the problem and fix it.
OP, what car and what light? Do you get an error message?

Well, the thing is that those lights actually sometimes really come on for no reason.

dr.fuzzenstein

CiniO wrote: »

Well, the thing is that those lights actually sometimes really come on for no reason.

Never happened to me so far. whenever a light came on in my car, it was there for a reason. That light on the dash was not put there by the manufacturer for no other reason than to annoy you and cost you money, it's there to show you that something went wrong and if you like your car, it's better to check it out. I know, it used to cost hundreds to bring the car in and have it diagnosed, but there is no need for that anymore, at least not for anyone who can pair a bluetooth device and install an app on a phone.

JohnBoy26

dr.fuzzenstein wrote: »

The attitude to warning lights and error messages in modern cars never fails to baffle me. The opinion seems to be they are just an annoyance that pops up for no reason other than to cause an inconvenience and they have to be reset or ignored.
The reason there is a warning light is because something isn't right, so the correct remedy is not to just make the light go away, but to find the problem and fix it.
OP, what car and what light? Do you get an error message?

My car is throwing on the light with the past year due to a lamda sensor. Still passes the nct though and it's going fine. I know I probably should change it but haven't had the time to get around to it.

dr.fuzzenstein

Special Circumstances wrote: »

I'm willing to bet on the country of the brand, and the brand family of the car ;-)

You're on! 50 internet points says it's French and Renault!

pippip

Out of curiosity....and not knowing much about diesel engines.....why do they fail with the light versus petrol?

Special Circumstances

dr.fuzzenstein wrote: »

You're on! 50 internet points says it's French and Renault!

My guesstimate involving popularity in Ireland, propensity for check engine light, expense of fixing likely problems... = VAG.
French, psa rather than Renault after that.
Renault owners are too wary of the inevitable jibes to ask about CELs.

biko

pippip wrote: »

Out of curiosity....and not knowing much about diesel engines.....why do they fail with the light versus petrol?

The manual for NCT states to not smoke test a car with a EML on.
https://www.ncts.ie/media/1004/nct-manual-july-2014.pdf

I'm not sure on the reasoning behind this difference. Possibly there could be some danger involved, a runaway engine or summat.

Kimbot

dr.fuzzenstein wrote: »

The attitude to warning lights and error messages in modern cars never fails to baffle me. The opinion seems to be they are just an annoyance that pops up for no reason other than to cause an inconvenience and they have to be reset or ignored.
The reason there is a warning light is because something isn't right, so the correct remedy is not to just make the light go away, but to find the problem and fix it.
OP, what car and what light? Do you get an error message?

Eh the Mazda RX-8 is known to light up like a Christmas Tree when everything is working perfectly fine from what I remember.

shietpilot

dr.fuzzenstein wrote: »

The attitude to warning lights and error messages in modern cars never fails to baffle me. The opinion seems to be they are just an annoyance that pops up for no reason other than to cause an inconvenience and they have to be reset or ignored.
The reason there is a warning light is because something isn't right, so the correct remedy is not to just make the light go away, but to find the problem and fix it.
OP, what car and what light? Do you get an error message?

Funny you mention that. When I was getting my tyres changed a guy pulled into the garage with a Bora and requested the mechanics to "disable the check engine light for the NCT". He was told the car needs to be diagnosed to see what the issue is but he rejected the diagnostics and asked them to disable it

jimgoose

shietpilot wrote: »

Funny you mention that. When I was getting my tyres changed a guy pulled into the garage with a Bora and requested the mechanics to "disable the check engine light for the NCT". He was told the car needs to be diagnosed to see what the issue is but he rejected the diagnostics and asked them to disable it

There's "Mate a' mine, he knows about cars, like, an' he says"-ism of the five-star, ocean-going variety. :pac::pac::pac:

shietpilot

jimgoose wrote: »

There's "Mate a' mine, he knows about cars, like, an' he says"-ism of the five-star, ocean-going variety. :pac::pac::pac:

Honestly though, a dual filament tail / brake light bulb melted both filaments joined together and caused a check engine light on my Focus. I can just imagine a typical motorist trying to turn the light off rather than actually fix the issue :eek:

jca

pippip wrote: »

Out of curiosity....and not knowing much about diesel engines.....why do they fail with the light versus petrol?

They don't. ABS or Airbag being lit will fail whether its diesel or petrol.

pippip

jca wrote: »

They don't. ABS or Airbag being lit will fail whether its diesel or petrol.

Sorry I only ment the engine mgt light.