Working on a 02 TJ throwing code p0051(oxygen sensor heater circuit voltage low bank 2 sensor 1). This orginally started when customer brought me car and 4 new ntk 02's and ask me to replace. I do so per the request. Upon clearing the codes this one remained. First thing i did was check the new 02 for the code specific bank(bank 2 sensor 1) to ensure new plug had not failed. All good. So i began in basic order. Battery to fuse . Fuse was good, moved on to hard start relay. Then to Heater circuit relay. All these tested Good. I decided to print the schematics and gather some direction. Since then I have followed down the circuit from the relays to the O2 sensor plug pin 1(heater wire) ohmed and passed voltage test. Moved on from plug to c103 ohmed and voltage test good. Moved from c103 to pcm c3 pin 16, voltage good. So i decided to compare to another sensor since the schematic control side tested good. Upon testing other sensors i found the sensor in question was missing ground on pin 2. Pulled ground schematics and tracing both ground 104 and 105 test good, cleaned and reinstalled anyway.was baffled so i jumped the ground to the battery. Boom all plugs have exact same readings. Retested circuit, still looks good. Clear code and start jeep. Code comes back 30 seconds later. So i figured maybe i need to jump the ground to the pcm as it controls ground for the circuit. So I jumped from o2 pin 2 to c3 pin 16 on pcm. No change. Can anyone share some insight on what im dealing with here? Is it the pcm? No other issues besides this.