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.

Pin 2 on sensor is ground for heater
Pin 3 is sensor ground to pcm

Try running a ground T-ed into sensor wire for pin 2 (on the wire actually connected to the sensor distal to sensor connector) to a good engine ground point

With only a single sensor heater code and a JTEC/jtec2 PCM very unlikely the pcm


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I will do so this evening. Around 6pm cst. Run from good engine ground to sensor with a T to the ecm pin 16?

Not to either pin but to actual heater ground wire (not sensor ground wire)close to sensor between sensor and its connector


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I am apologetic can we include pin numbers or something, trying to understand what your suggesting but im having a hard time. Maybe due to context

The oxygen sensor connector has 4 pins
A power wire to heater aka heater control (pin1)
A ground (pin2)
A sensor ground aka sensor return (pin3)
A sensor signal (pin 4)

Want to T into the ground wire as it supplies ground for the heater circuit




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If i understood you correct no change. Light came back on.

Bump

Vehicle now has p0051 and p0151 and a random high idle. All test perforned show correct wiring. And good sensor.

What were the original codes before you first cleared them?

Were any of them the P0051 &/or P0151??


You appear to now be getting low voltage codes for both the heater & the sensor circuit of the 2/1 sensor.

Have you tried putting that old sensor back in to see if the same codes come up?

Have not due to order of events customer took vehicle in between for 3 days and disgarded original sensor. Both codes were existant before hand as i didnt clear till after i swapped sensors.

Update For those having the same issue as I had. I ran through the entire circuit and tested good everywhere on the schematic. So I came to the conclusion that pin 16 in the ecu had a burned solder connection. Informed customer that ecu was cause of problem. Ordered ecu and installed. Codes are gone jeep runs perfect.

Thanks for posting results. These types of codes are tough to pin down & fix.