I have a 2010 f150 5.4 and engine light came on code was bad o2 sensor so I replaced all 4 engine light went off. 3 days later engine light is back on what could be causing this?

 

what code did you get? o2 sensors are often needlessly replaced

 

If I was a betting man, no doubt OP is another one of those cases....lazy diagnosis, change part just because, scratch head in wonderment.

 

 

Ah yes a circuit code, you need to check all the wiring, make sure you have good power and ground and signal circuits

That code does not automatically mean the sensor itself is faulted

 

There is no code whose definition is "bad part". READ what it says (your photo doesn't show the definition, but you can see it on the paper) and think about it before reflexively buying/replacing parts. It says there's some problem with the CIRCUIT, which DOES run through the oxygen sensor, but not exclusively. The circuit also includes several wires & connectors, and the PCM. The fault(s) could be in any or all of them, so you have to do some diagnosis FIRST. Step 1 is always: does the indicated condition exist? If it doesn't, then the fault is either intermittent, or it's inside the PCM. Either way, throwing 4 oxygen sensors at it isn't likely to fix a circuit fault for ONE of them. I hope you kept the originals because they're probably higher quality than the replacements, and obviously, there's nothing wrong with them.

 

Yes I still have the original o2 sensors still they are the originals so I guess I’ll check all the wiring and grounds. I really don’t know where to look though under hood under the truck

 

Then how are you going to check them if you don't know where they are? If you don't know how to do this diagnosis, pay a pro. If you want to learn how, start reading, and watching YouTube videos about how to use a digital multimeter to check automotive wiring.

But before doing all that, LOOK AROUND under the truck, especially along the exhaust system between the engine & the first cat (on the side indicated by the fault). I don't have the specific definition for P0150 on your truck (and you should put ALL its details into your signature so we can review them with each reply), but on some vehicles, it can mean that the sensor response doesn't change. That CAN be due to exhaust leaks, which are fairly easy to see & hear - they're even easier to hear if you plug the tailpipe on the idling engine & crawl around underneath. Ignore the leaks from the muffler - they're built in, and are too far downstream to affect any oxygen sensor.

 

Yes I want to learn. So I will check all the wiring and check for any exhaust leaks. Everything seems to be working fine I just don’t like seeing the engine light on. Thank you for all your help.

 

How many miles?

https://www.obd-codes.com/p0150

"Causes
Usually the cause of P0150 is a bad oxygen sensor, however this isn't always the case. If your o2 sensors haven't been replaced and they are old, it's a good bet that the sensor is the problem. But, It could be caused by any of the following:

Water or corrosion in the connector
Loose terminals in the connector
Wiring burnt on exhaust components
Open or short in the wiring due to rubbing on engine components
Holes in exhaust allowing unmetered oxygen into exhaust system
Unmetered vacuum leak at the engine
Bad o2 sensor
Bad PCM

Read more at: https://www.obd-codes.com/p0150
Copyright OBD-Codes.com"