Just closing off this thread, hopefully that's it fixed.
As mentioned the i3 has 10 parking sensors in total. 8 are PDC sensors and 2 are PMA sensors (park manoeuvre assistant) if the car is equipped with this technology fitted on the front wings/fenders. It's a bit of a gimmick if I'm honest. My wife rarely uses the tech, but the irritating thing is, if one of the PMA sensors is defective the whole lot is down, and the park PDC error chimes up on start-up, in some cases you look park distance control too.
So it's been a bit trial and error. I purchased a new PMA sensor (Valeo) and prior to fitting it - I scanned the car. The error showed it was front outer right. To check, I swapped the sensor with the other side and the fault followed when it was scanned again, so I was certain the PMA sensor was defective.
I painted the sensor with a card template, alcohol wipe, two coats of plastic primer, two coats of colour and three coats of lacquer once it flashed off. All fitted and rescanned. The error came back. I checked the wiring, used contact cleaner and plugged and unplugged the union where the wiring connects with the PDC sensors.
That got me thinking, that if one PMA sensor was defective, then as it effectively uses the other to complete the circuit, there was a good chance the other could be failing too. The car is 2015, so not unreasonable.
I purchased another Valeo PMA sensor and installed this on the other side. I rescanned the car and all the codes are gone in ISTA.
Anyway - hopefully that helps if you encounter the same issue. It's very frustrating, but worth it in the end.
2015 i3 REx, 60ah, solar orange. Reversing camera, leather interior, sunroof, park assist, professional navigation.