Update:
Followed some of the HEGO tests that didn't require a breakout box -

Check resistance of heater element on HEGO
Measurement between Key power and Power ground on the O2 sensor with a cold motor was 3.6OHMS. Specs call for between 2.0 - 5.0 at room temp so it passed

Check for power at HEGO harness connector
Measurement between key power and power ground on the o2 sensor vehicle harness connector was 12.5V. Specs call for greater than 10.5V so it passed

Service code 42/92 fuel control always rich: Check hego signal for short to power
Measurement between hego signal and power ground on the o2 sensor vehicle harness connector was .05V. Specs call for less than .5V so it passed

Check hego sensor for short to ignition run circuit
Measurement between Key power circuit and HEGO sig circuit at the hego sensor connector was OL(open loop). Specs call for resistance greater than 10,000OHMS. so it failed

Motorcraft o2 sensor en route https://www.rockauto.com/en/moreinfo...pt=5132&jsn=27

 

Tests are only useful if done in-order. The page you posted clearly says to disconnect the HEGO, and to then probe the sensor side of the connector. I've never used a breakout box. When the procedure refers to one, it simply means to probe the indicated circuit. Find the function of that BOB pin (usually the same number as the EEC pin it's connected to, but often called out by function &/or wire color) and pierce-probe the corresponding wire. I use Pomonas.

 

Got it - will back up and do the tests asking for a breakout box with your pierce probe method.

Those tests were all done with the HEGO disconnected. some of the tests were probing the connector side / some were probing the harness side.

 

Hey Steve -
Where might I find a diagram showing the BOB pin functions? I just got that same set of pomonas in the mail, do i just test from as close to the eec connection as i can to the far end of the same circuit?

 

There isn't such a diagram AFAIK. As I said before - there are hints in the instructions as to what you're really doing when it refers to the BOB pin. But the BOB pin number is usually the same as the EEC pin.

(click this text)

 

Gotcha thanks!
So for example this page below states for truck w 4 wire hego (what i have)
"Measure resistance between test pin 49 and test pin 46 at the BOB and HEGO GNP at the HEGO vehicle harness connector" Check for less than 5.0 ohms at 200 ohm scale

Does that mean I
1) probe 49 and 46 to check if theres resistance
2) probe 49 and the HEGO GNP (what is GNP?) at the harness connector.

EDIT:
I have continuity from pin 49(orange) to the o2 harness and its ohming out at .8
I have no continuity from pin 46(grey/red) to the o2 harness and my dvom is reading OL

According to the wiring diagram, there is a pin 49 and 46 have a junction before reaching the o2 sensor harness



I jumped the grey/red from near the 60 pin connector into the orange line to the beginning of the o2 sensor harness and got continuity and .8 ohms. I'm assuming this means i have a break wherever the 2 lines join before reaching the o2 harness?

 

All tests for "<5 Ohms" are testing continuity of the circuit (no breaks in the wire; no unplugged connectors, etc.) And as you deduced by studying the wiring diagram, that test is for the 2 EEC pins (which correspond to BOB pins) that should be connected to the HEGO at its return (ground) wire. So you put one probe on that HEGO GND wire (AT the HEGO before its connector) and use the other probe to check as close the EEC pins as you can get.Remember that ANY document can have errors. Look at the context, and the other steps in that section - they're all about testing the HEGO GND circuit. The P is a typo.Yes, that's the correct deduction from the information you POSTED.

 

Gotcha thanks - sorry I know I posted it, edited the reply after I finally figured it out.
Thanks! Didn't realize the GNP / GND was just a manual typo.

I'll start opening the harness up to see where the HEGO Ground and the Signal return join. Is it typically just a splice or is there some sort of connector I should be looking for?

again thanks for all the help!

 

The Copper strands are resistance-welded together, and then taped up as the harness is being assembled.