Engine warning light on Citroen Xsarra Picasso has come on

I went out in my Citroen Xsarra Picasso (Diesel, 1.6, 10 years old) this morning and the car started fine. However, after driving for around 3 minutes, and when going around a corner, the car steering wheel seized up on me and some of the lights lit up on the dashboard - ones for the battery, oil and another one (not engine one). I parked up the car and even though it turned over, it would not start - then all of the lights went out and a message came up on the dashboard, saying 'engine problem'. My son checked the oil and it is fine, so is the battery as it's quite new. I managed to get the car started and then drove it home, with just the engine warning light lit up on the dashboard and a message appearing saying 'engine problem' - beeped a bit as well.

My son says it will cost me around £80 to get a fault diagnostic on a machine done, but that if my garage want to take out the engine, to forget it, as the labour alone for that would be hundreds of pounds. One thing I will say though, is that a couple of weeks ago, my son noticed that there is not an air intake box fitted at all, just part of a pipe that is hanging loose. Do you think that dirt could have been sucked in and perhaps caused the problem? I've had a read on some message boards about the engine light coming on, and some people have just left it and even said that the Citroen dealer they contacted, also told them not to worry about it! I think that my son thinks that I should just go ahead and get rid of the car without even paying out for a fault diagnostic check. Any ideas on this please, as I have work booked in at a town around 16 miles away from me next week and don't want the car to pack up on me. Thank you.