My 2017 F150 3.5 EB has almost 43K miles and kicked out 3 codes - P0301, P0316, and P21CF. I cleared the codes and replaced all spark plugs (they looked pretty burnt/black). Started it back up and still a rough idle at first and the P21CF code returned. Cleared it again and it came back. I have searched everywhere but couldn't find any information on this code or if I should start looking at fuel injector replacement. Please help! Thanks!

P0301 - Cylinder 1 misfire
P0316 - Misfire detected on Startup
P21CF - Cylinder 1 Injector B Circuit/Open

 

that means ijector 1 port injector oper circuit can be the wire or the injector.

 

remember you got 12 injectors now

 

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All the codes are associated. >> affecting cylinder #1.
316 tells you the computer detected (a) misfire.
301 the cylinder # that it was detected on (1).
21cf, the trouble is electrical, as an open circuit for cylinder #1 fuel injector.
The first three are detected from crank rotation time becomes too slow.
The last one from electrical current flow; the normal signature detection was not correct or missing.
I would not jump on replacing the injector until you're sure the plug and wire harness is not the fault.
Good luck.

 

My truck is throwing the same codes as you listed. How did you end up fixing yours?

 

Were either of you able to correct this issue? I am getting the same code and trying to chase this down now. Any help would be greatly appreciated.

 

Im throwing the same P21CF code, im at 146k miles. Not sure if I should replace all 12 injectors if im gonna dig in and open it all up. Mechanic said it B circuit so all of the A injectors need to be removed and unable to inspect the wiring or the harness until taking it all apart. What was the issue for the few others on this thread, did you end up replacing the injectors?

 

READ the comments above, especially the one from @Bluegrass. Your problem is likely electrical, inspect your wiring.

Always remember to post as much information as possible:
Year, Mileage, Engine, Trim, DTCs, etc. The more information you supply, the better the help will be. Noone here is magic. It is up to you to do the leg work. Also, the solution is not always easy. If it was, there wouldn't be any professionals to rely on.