On the way in to work this morning my CEL came on. I had left the car running for about a minute and then started driving, but off boost for about 5 minutes until everything came up to temp. It was while driving off boost,just after changing up into 5th that the CEL came on. About 4 weeks ago, it happened but during normal driving conditions. It went off the next day and when I got the code pulled, it was the lambda sensor that had caused this. I won't be able to get this code until Monday but I was wondering if anyone had any ideas. It's still driving perfect, no noises or stutters. Really dunno what it could be. Thanks in advance.

 

It can be the lambda sensor if you didn't replace it

 

As it seemed like a one off, we cleared the code and left it to see if it happened again. Its been about a month without it coming back on but liker I said, I can't check the code till tomorrow.
If it is the lambda again, what could be causing the problem and could it be expensive?
When we cleared the code before, her asked me about the fuel I use and was I giving it the beans. I think last time it came on, I was going for it a bit and I had to use Tesco's momentum. I usually use shell but this time I was all back to my usual. I don't have a clue