No spark no fuel.

[Richard_TD]

I thought there might be some kind of sensor that wouldn't allow fuel supply or spark if the cam wasn't where it should be. I'm not entirely familiar with modern engine systems though.

Not all engines clash when the cam belt goes, though I'm not sure if yours is an interference engine or not. The tell-tale is if the engine turns over at a constant speed instead of the pulses you normally hear when you turn an engine over on the starter. As you say, it shouldn't be the belt after 3000 miles- though it's possible something has come adrift after the belt change.

It does sound like you need to get the codes read.