Vauxhall Vectra 2.0L 16v P0130 O2 Sensor Low Voltage Issue - Diagnosis and Solutions

Hi everyone, I'm reaching out for expert advice as I've just purchased a Vauxhall Vectra 2.0L 16v model and am currently experiencing an engine management light issue with fault code P0130 — O2 sensor low voltage. I’ve used OPCom diagnostics to monitor live data during cold starts. The O2 sensor reading fluctuates between approximately 0100mV and 450mV, indicating it's operating in closed loop for about 10 seconds before the voltage drops to zero. Throttling the engine causes a switch between open and closed loop operation. I’ve visually inspected all wiring harnesses for chaffing or corrosion and found no issues. I previously had a pipe leak from the purge valve (now repaired) and replaced the O2 sensor with what I believed was a good-quality used unit, but the P013-0 fault persists. Upon removal of the original sensor, I noticed small white patches and overall light brown discoloration — signs of aging or thermal stress. The replacement sensor I reinstalled had significant carbon buildup, which I cleaned manually. Despite these efforts, the problem remains. What should my next steps be? Any insights into potential underlying causes? Thanks in advance for your help — this is a very frustrating issue to troubleshoot on my own.