2004 2.5 tdi VW lt 28 brake issues

I have a feeling the previous owner may have removed a bulb or two from the dash. How long have you had the van?
There should be four abs sensors and the pain in the arse bit is they are a nightmare to remove (when they're fitted) and they are hard wired into the ecu, when replacing them the original wiring has to be cut and then join the new wiring/sensor. I fitted a weatherproof connector plug on my new sensor rather than hardwire it up again just for future convenience if the knuckle ever has to come off. I couldn't remember which warning light came on when the sensor was removed so I've just unplugged the abs sensor and checked, it's the immobiliser light (the yellow light on the right with the circular arrow) which comes on and stays on solid.

The only thing left is the servo! If that doesn't sort it.... a can of petrol and box of swan vestas should haha.

If you pump the brake pedal with the engine off does it stiffen up, if it does, keep your foot on the pedal and start the engine, you should feel the vacuum assistance help draw the pedal lower.