Emissions warning light on dashboard.

[Hewlett81]

I have a Vauxhall Astra Sri 113 on 60 plate. I got in this morning 13/04/14 and started it up as normal, I noticed that the emissions warning light was on constant, where as it would normally go out when the car had started. I have noticed that the car was chugging quite a lot, but there was not much loss of power, I bought the car from the trade centre wales, they have told me it does not come with any kind of warranty. Since I have had the car I have only done 1500 mile in it, it has just clocked up 40,000 miles this week. Have you any idea what the problem could be with regards to the light being on?

I have done the pedal test and the error code was 030401, which I read on the internet was a misfiring in cylinder 4.

Many thanks

Mathew.