Have you just fuelled up? Sometimes it does that, give it a spirited drive to clear any carbon and see if that works!
Please don't take this that I know anything about cars at all and if your van goes bang it's not my fault. Getting someone with a plug in cable will tell you any fault codes!
My engine management system light cam on so I called into a VW dealer who did a quick computer check and said it was the exhaust temperature probe. Told OK to drive to my own dealer,a about 250 miles who then replaced (I think) a sensor.
Mine came on a couple of days ago. Have just taken it to the VW dealer ( Perigueux, France) who did the diagnostics which showed up a faulty glow plug on No4 cylinder. It's not serious ( although it may be more difficult to start in cold weather), they have reset the warning light and have booked me next week to replace all 4 plugs. Hope this helps
I have had this same fault for over a year, light was on, then a motorway run it went off for a while. Finally got sick of it and booked T5 in to get it sorted. New sensor fitted 4 weeks ago and the van is running sooooooo much better, wish I had it sorted sooner. The sensor was only about £15 + fitting so why bother just sort it.
Turned out mine was because the door lock / sensor had packed up... which explains why it was deadlocking with me inside if I didn't start the engine as soon as I got in, and the headlight-left-on warning was no longer working.