Good morning rdrp,
Did you fix the car? I have the problem as you. Changed the upstream sensor with NTK 25712 and the same fault came back after 3 warm ups.
- 8.5v on the heaters pins, EMS-2 fuse is OK. Average current during start up is 4-5 Amps.
- heater resistance measured 5-8 Ohms (depends how hot it is)
Thank you in advance.