1996 Ford Bronco 5.8L O2 Sensor

I have a CEL for a Bank 2 (upstream) O2 heater sensor fault. I will update with exact code name/number. No other DTCs are present. This is the only O2 sensor on Bank 2. Bank 1 has an upstream and downstream O2 sensor and both are good. I'm in California so I have to get this fixed to pass smog. Also, I'm a novice at this stuff so feel free to include basic info.

Here is some amplifying info:

-My O2 sensors have four wires. 2 for the heater and 2 for the signal.
-I did a voltage test on the heater circuit and have 12 volts at the O2 plug.
-My scan tool shows the signal wire reads lean at .2v while my two other good O2 sensors read normal values with engine running (approx .2 to .85v)
-I have backprobed the signal wire at the on the plug of the Bank2 O2 sensor and voltage fluctuates from approx .2 to .85v (same as my other two sensors).
-I then backprobed the bad O2 sensor wire at the PCM and it still reads .2 to .85v going into the PCM.
-The O2 sensor tests good. Tried swapping it out as well.
-Tested all PCM grounds at the PCM by checking for continuity between the ground pins and the body groud.
-There is only one battery power wire that goes into my PCM according to my wiring schematic and that pin tested good as well. (12.5v from pin to ground).
-Visually inspected all pins at PCM and none of them are bent or missing.
-I've looked for shorts on my wiring harness using contact point strategies seen in your videos and did not find anything.
-I then pulled the entire engine wiring harness to visually inspect all wires with wire loom and tape removed and could not find any bad wires. I have not pulled one portion of the harness that goes under my intake manifold yet, but I will have to pull the intake to do that. This section does have a common red wire that is used my the O2 heater circuit and the fuel injectors. Also shares a grey/red wire that is shared with all all O2 sensor signal circuits.

Here are my initial questions.
1. Why does the DTC show up as a O2 heater ciruit issue when the heater cicuit tests good, but the scan tool shows lean (.2v). Seems like I should get a code that reflects lean Bank 2, but not sure if ford has one.
2. Why would my scan tool show a steady .2v when the O2 sensor is actually reporting .2 to .85v according to my multimeter. I'm thinking the PCM must be getting shorted out by some other circuit?
3. Can someone confirm correct wire for a 5v circuit test? I'm thinking I can test some other sensors that use the portion of my wiring harness that runs under my intake manifold which is difficult to visually inspect. I have one common red wire on all 3 O2 sensors that powers the heater side of the sensors. The other common wire between all O2 sensors is a grey/red wire on the signal side of the O2 sensor. I'm assuming this grey red wire is the 5v ref wire that I need to test? I beleive the other unique colored wires on the signal side of the O2 sensors are the signal wires because they are reporting the fluctuating voltage.
3a. Should the 5v reference wire of the O2 sensor be reporting close to 5v at all times when key is in run position?
3b. Should the 5v ref wire change voltage when engine is running?

Appreciate any guidance you can provide.

Cheers,
Nate

I have a CEL for a Bank 2 (upstream) O2 heater sensor fault.

Is that a Heater Sensor or Heater Curcuit Fault ????

-My O2 sensors have four wires. 2 for the heater and 2 for the signal.
-I did a voltage test on the heater circuit and have 12 volts at the O2 plug.

You only need to look for battery Voltage ( PWM) & Ground at the HEATER Wires, Ignore the 2 signal wires ?? Now, getting Voltage is not enough !! Only Proves that the Heater is being asked to operate, the heater may be worn, shorted, open in the 02 sensor.
You need to use an amp clamp and scope to monitor that.

It is likely that the Heater is PWM switched either on the + or - side. Establish that then Scope the Voltage & Current, Compare to the Good Side ??

1. Why does the DTC show up as a O2 heater ciruit issue when the heater cicuit tests good, but the scan tool shows lean (.2v). Seems like I should get a code that reflects lean Bank 2, but not sure if ford has one.

Im not convinced that you have tested the heater Circuit Correctly !! See Above

2. Why would my scan tool show a steady .2v when the O2 sensor is actually reporting .2 to .85v according to my multimeter. I'm thinking the PCM must be getting shorted out by some other circuit?
3. Can someone confirm correct wire for a 5v circuit test? I'm thinking I can test some other sensors that use the portion of my wiring harness that runs under my intake manifold which is difficult to visually inspect. I have one common red wire on all 3 O2 sensors that powers the heater side of the sensors. The other common wire between all O2 sensors is a grey/red wire on the signal side of the O2 sensor. I'm assuming this grey red wire is the 5v ref wire that I need to test? I beleive the other unique colored wires on the signal side of the O2 sensors are the signal wires because they are reporting the fluctuating voltage.
3a. Should the 5v reference wire of the O2 sensor be reporting close to 5v at all times when key is in run position?
3b. Should the 5v ref wire change voltage when engine is running?

Sorry to Pee on your fire here buddy but the Heater Circuit will be PWM Battery Voltage, The lower Voltages you are looking at are not the Heater Circuit, For now, ignore them please !!!

On a 1996 vehicle I guess these are old School Sensors (not wideband) , Titanium or Zirconia - Lots of reading on the net about these.


With both Upstream sensors unplugged you could measure the resistance of both sensors across the HEATER Circuit ONLY - Then Compare,

Is it possible to swap the 2 sensors ?? Look for the fault code to change to the other bank ???

Hello Again

I just Googled
"Scanner Danner 02 Heater Circuit" and a few things popped up !! take a look !!