So my car threw the code P0030 last week, referring to an issue with the pre-cat O2 sensor, made sense considering I had only achieved 400km from the last full tank . Removed the old one to get the part number. Bosch and Denso list them for $200+ a piece, yikes! Found cheaper unbranded one from an eBay for $75. It's a simple small part, surely price won't affect quality too much, maybe it'll just last shorter than an oem one.
Received in the mail, wrapped in a plastic bag with two torn cardboard pieces either side for "protection". Went ahead installing it, erased the previous codes and started the car. Got two codes, P0030 again and P0032 (O2 sensor circuit too high in voltage). Went to compare the new and old senors. The difference was the wiring. There are four wires: a white, a blue and two blacks. The two blacks are for the heater circuit. The two black wires on the new sensor were on the bottom two pins of the connector, THE OPPOSITE to the OEM one. Even after taking the new connector apart and swapping the wires i got the P0030 code back (likely the wrong wiring had fried the new sensor)
I am unsure if this has caused damage to the heater circuit, I have read the P0030 can also mean the relay for the circuit is busted or even the fuse within the ECU (meaning I'll need a whole new one)
For now I have plugged the old sensor in place while I get a refund from the ebay seller. But hope this serves as a useful warning to anyone with the same issue