I was reading the Trans cooler line when I noticed I had an unplugged 02 sensor on the passenger side right under the passenger seat. I was trying to find the other end to plug back in but no luck. I was able to find the harness where the other o2 sensors are plugged into. Is there one main harness that all the o2 sensors run into or should I be looking for something else???

 

What engine? Do you have a CEL? If so, post the codes.

 

If it's a rear sensor, it won't affect the way it runs. All it does is monitor the cats for efficiency. The front sensor close to the exhaust manifold is what the PCM uses for control. You should have codes.

 

The Engine size is 5.4. I don't have a CEL, I do have a SES light and an ABS ligh On.

 

SES=CEL=MIL. Same thing.

What are the fault codes?

 

That looks like the front sensor, not the rear sensor. That will definitely affect the way it runs adversely.

Scan the OBD2 and post the exact P-codes.

 

These are the faults that I was able to pull off the truck.

 

You have issues with all 4 O2 sensors.

 

Where should I start to troubleshoot these issues?

 

Google those codes and read the instructions.

 

https://www.obd-codes.com/p0135

https://www.obd-codes.com/p0136

https://www.obd-codes.com/p0156

https://www.engine-codes.com/p1131_ford.html

Bank 1 is passenger side, sensor 1 is the front sensor.