I recently have come across the same exact thing on my 2000 VW golf 2.0, 2 universal o2 sensors (went cheap), the (4) wires matched colors exactly, soldered them in and I got the EXACT same codes you did... low volts- both sensors- bank 1... I did exactly what this guy has told you to do... I used less of a solder- divided and cut about half the wire off all my ends of the wire (even the heater wires.. why not..) by splitting the wire ends into 2 equals and cutting (very easy) USE SOLDERING PASTE BECAUSE YOU WILL STRUGGLE LIKE CRAZY WITH OUT IT!!!! <-- that part is very very important... shrink wrapped and silicone put both sensors back in my car and it worked like magic gas mileage back to normal and then some
.. --BEWARE--- if your coolant temp gauge is acting up you WILL DEFINITELY HAVE THE SAME EXACT CODES in conjunction with a P1256 code which on a VW means coolant temp sensor.. Autozone's code reader throws air to fuel metering as the err, so thank the Germans for letting you know your using more gas because you temp gauge don't work right