Need help with A4 1.9 TDi 130 'Safe Mode'

Hi,
Recently purchased an 2004 Audi A4 1.9 TDi 130 with 114k miles from a used car dealer. Car is okay, but every so often, it goes into 'Safe Mode' and the hazard lights flash on (usually when the ignition is on or if the car is stalled). Had the car looked at and it's coming up with a fault code from immobiliser communication and the immobiliser control module itself.

This morning, I came to start the car and it just kept turning over but didnt start. To cut a long story short, called the AA and they finally got it going but it was coming up with a fault code for the crank sensor and low fuel pressure. The car is back at the dealers but I dont think they know what they're doing.

Just wondered if anyone had had either of those faults and whether they could be related?

Thanks,
Joe.