Welcome to the forum. Hopefully someone else (Fordem??) will come in to advise on this. To be honest, I had never heard of a U2001 trouble code before, but found that the U codes between 1000-3000 are manufacturer specific (as if you google this, you can also find that it means different things for other manufacturers). In any event, every single hit I got for this code seems to have come from India, for the Maruti Suzukis, for some reason. In any event, I did finally find one video that might explain what’s going on….basically that in your vehicle, there is communication between the ECU and alternator, via a LIN bus, which means Local Interconnect Network which is a communication between different components in the vehicle, via a single wire. The ECU and alternator in your car are communicating via this system, and one of those pathways (ECU to generator, or generator to ECU) is malfunctioning. From what I understand, this can be anything from that single wire fault, bad connection, or bad ECU. The video that I found (where the Indian mechanic actually speaks English) is here, and (if I’m correct in all of this) you may want to show it to your mechanic:
