ECU is Engine Control Unit (or Module). With the fuse blown, it will cut power to the engine. There is a diagram on the fuse cover that shows what each fuse controls.
This has the diagram, but it could change over the years. Start with unplugging the electrical connector to the ABS. The brakes will still work, but the ABS will not. Also, check the reverse lights and speedo.

Fuse box diagram Volkswagen Passat B5 and relay with assignment and location

The designation of all fuses and relays Volkswagen Passat b5 with a box diagram and photos are examples of their performance. Fuse for cigarette lighter and fuel pump.

fuseandrelay.com

 

Thanks PZ,

For the electrical connector to the ABS, I assume you meant the tab connector behind the rubber grommet accessed from the wheel wells? Or is there a simple fuse or relay connector that you meant.

speedo, reverse all working well. My diagram card has the “ABS” pictogram for fuse 7. So I am guessing that it is related to ABS. No ABS light on however. I do sometime get the small exclamation point with the reverse circle arrow around it illuminated.

 

It's attached to the ABS unit by the p/s reservoir. It's two plugs I think, the lock-tab slides off the end a bit before you can pull the plugs away. It will disable the ABS, so if that is what is shorting out the fuse, I guess it's got something else on that circuit.
Do you have access to VCDS? It might give more information than I can think of right now.

 

Well, the fuse has blown again. I have two teen boys who have been using the car and now it is at an Autozone and won’t start.

They pulled the sensors from each wheel well to see if there was a short in them. But now they are saying the fuse pops immediately. Now -I was under the impression that one could remove the abs sensors from the clips in the wheel wells and the car would still start. Or is that not the case?

they haven’t tried to undo the plugs at the ABS module as it was late and they needed to get home. Is that the next place to try?

one thing that did change is that the “Brake Pad Wear” light is also on. Guessing this is either part of the ABS sensor or they knocked this sensor when pulling the ABS sensors?

I still don’t quite understand how the car was running with a 5 amp fuse in the ABS (fuse 7 - 10A) spot. But now the 5amp fuse is blowing at key turn.

this is driving me nuts.

 

Oh and yes - there is a VAG com in the car, but it often just says “cannot connect to ECU”. And I am not sure what to tell the boys to look for with it.

 

Yes, unplug the ABS under the hood. I can't recall what the fuse is for the sun visor, but they were known to short out. You can also check the glovebox light and the puddle lights at the bottom of the door card.