Is it possible supermarket fuel causes engine management light to come on, on Sprinter?

I just bought a van from a reputable garage.

I test drove it on motorway, through city, etc and it was perfect. One day ago.

Today the guy come to to drop the van off to me… I drove it on the motorway no problems at all for 10 / 15 miles. Then I went to a Sainsbury’s to fill up, turned around and headed home. A few miles into the journey home, the engine light came on.

I rang the guy up and he said it’s possible because it’s been serviced today but he is very confident it is because I used poor quality diesel. Is this viable?

He said he guarantees nothing is wrong and has invited me to drive to his tomorrow to plug in diagnostics. It’s a long journey so I’d rather not go if I have to.

What do you think?

P.s. the fuel cap is not loose and I 100% filled it up with diesel