02 sensor/ENG1 fuse circuit. Elect Gurus - help please!

[Vodka0tter]

I am not sure if I have a problem or not. I went in for a tune this spring and the tuner guy says your odbii is dead. I locate what I think are 2 shorts in my wiring. 1 in the cab - I have located that one. While looking at the power dist. box (fuse box under the hood) I note that many of my fuses and the "always hot" posts have a circuit to ground (ohm meter beeps...) Note - the battery is out of the truck at this point.

I locate the source to the 20A ENG-1 fuse. I pull it - no ground circuit. Its a pink wire that runs directly to the driver side up-stream 02 sensor. Not tied into any other wire or circuit (I dont think). I disconnect the o2 sensor - the ground loop goes away. I replace the 02 sensor and still have the same problem.

Any input is appreciated.

Dale

You must be registered for see images

You must be registered for see images

View media item 32383
View media item 32384

 

[R422b]

Not knowing for sure what sensor you have I believe that is the sensor heater and it should always be connected to ground. It heats the sensor to bring it up to operating temperature quickly.
What was the actual resistance to ground?

Sent from my moto g(7) play using Tapatalk

 

[Vodka0tter]

It is part of the heater circuit...

 

[Vodka0tter]

So pink hot from the fuse box should show ground if it’s the heater circuit on an o2 sensor? Also grounds out all other circuits on that buss bar. Seems odd but I know little about circuitry

 

[delta_p]

The pink wires go from the Eng1 fuse go to ground through heater resistors. There should be continuity to ground through resistors.

if you measure the resistance at the fuse to ground its probably about 2.8 - 4 ohms, which would be the four "cold condition" 11.2-15 ohm heater resistors in parallel.

 

[Vodka0tter]

Perfect! It’s 12.2.

thanks for the help guys, appreciate it!!