E36 318is M44B19 O2 Sensor Circuit

Hi all,

New to the site. I own a 1997 E36 318is with an M44B19 engine. I'm currently have issues with DTC P01030, it's flagging up a malfunction in the o2 sensor circuit and I've just replaced the lambda sensor. It has one 4 pin pre-cat lambda sensor and I can't find a wiring diagram for that circuit online so I've no idea what wire corresponds to what. Off two pins I'm reading 14v and 0.72v so I'm inclined to think there's 2 grounds, the heater circuit (ok) and the signal circuit (not ok). If anyone could confirm this it would be a serious help.

Thanks,
Danny.