[Gremlin85]

The clunk you hear is normal. From what I understand, upon a cold start the Bypass Valve is pretty open as well as waste gates as the engine is running at a high idle for a cold start condition. Then, as the engine reaches a certain temp and RPM drop, you get the clunk of the bypass valve. Or it could be the wastegate. I forget which. Point is, it is normal.

As for the code.....

P0131 FORD - O2 Sensor Circuit Low Voltage Bank 1 Sensor 1
Possible causes:
Faulty Front Heated Oxygen Sensor Bank 1
Front Heated Oxygen Sensor Bank 1 harness is open or shorted
Front Heated Oxygen Sensor Bank 1 circuit poor electrical connection
Inappropriate fuel pressure
Faulty fuel injectors
Intake air leaks
Exhaust gas leaks

Tech notes:
Replacing the O2 Sensor 1 usually takes care of the problem

When is the code detected?
The voltage signal from the sensor is lower than the specified time.

Possible symptoms:
Engine Light ON (or Service Engine Soon Warning Light)
High Fuel Consumption
Excessive Smoke from Exhaust

P0131 Ford Description The front heated oxygen sensor (or O2 sensor 1) is placed into the exhaust manifold. It detects the amount of oxygen in the exhaust gas compared to the outside air. The heated oxygen sensor 1 has a closed-end tube made of ceramic zirconia. The zirconia generates voltage from approximately 1V in richer conditions to 0V in leaner conditions. The heated oxygen sensor 1 signal is sent to the Engine Control Module (ECM). The ECM adjusts the injection pulse duration to achieve the ideal air-fuel ratio. The ideal air-fuel ratio occurs near the radical change from 1V to 0V.

Read more: https://www.engine-codes.com/p0131_ford.html

::EDIT::
In other words, your passenger front O2 sensor closest to the turbo is getting low voltage. Most likely it is bad and needs replacing, but using the above information to diagnose the exact issue is recommended before just throwing parts at it.

 

[Gremlin85]

Hey there guys, very good read on this thread. My 2013 (108k miles) started throwing this code a while back and I replaced the bank 1 sensor 1 O2 sensor and it wasn't which a big deal. I used my SCT tuner and to reset the engine light and it seemed all good. Drove to work this morning (30 miles) no issues. Went and ran a few errands at lunch and boom its back on. I checked all the air intake connections and everything looks good and tight there. I guess my question is should i take it to the dealer now to get the injectors and fuel pressure checked or what should be my next approach

I would start looking for an exhaust leak first. You might have a leak at the turbo or at the exhaust manifold where it connects to the head. If your truck has any type of extended warranty, I would bring it to the dealer. If not, try searching for the leak first and go from there.

 

[Gremlin85]

Very good point, I did just have the passenger side exhaust manifold changed out by the dealer and this light kicked on close to 1000 miles later. It broke the rear stud off the manifold and caused it to warp.

Since they were the last ones in there, I would DEFINITELY bring that back and explain to them that the light kicked on after they were done working on it. Maybe it is leaking, maybe it's just a coincidence and the sensor is actually faulty, maybe it's something else. Let them make it right since they were in there last.

 

[Gremlin85]

Bank 1 is the passenger side of the engine. Cylinder 1 is the first one on that side closest to the front. Bank 2 is driver side.

 

[Gremlin85]

Nice, hopefully no more codes. Ever.