Hello and help. I have a 2003 F150 screw lariat 4x4 5.4L 3.73ls. This problem has been going on for the last 3 months. First time ces light came on it thew codes P0306, P0316, P0175, the dealership changed all the plugs at a cost of $560.00. The second time it thew a P0175 dealer said it was a wet o2 sensor, cost $125.00. Third time it threw a P306 so I changed the cop myself. Ran fine for a couple weeks and now the light came on and threw a P0306, P1152, what do I look for now? Please help.

 

Your dealer has to do more indepth analysis of the problem or have some luck.
Here is an analysis of the issue based on your previous codes and your present codes.
The 306 code keep reappearing and may be a key. (injector) cylinder 6.
The 175 and 1152 codes are just the results of the root cause.
The codes are complaing of a rich condition on the fuel tables.
With that as the basis, the following should be looked into.
Fuel system: Leaking injector, high fuel pressure, faulty regulator etc.
Other possible causes are air leaks, Ox sensor harness crosses, shorts.

This is based on the 1152 code because it is a test the PCM does on monitoring the Ox sensor switching time and suggests there is a fuel problem of some sort this test is picking up on.
Your dealer has to do a bit more than surface work to get the root cause by considering all the codes and what they are representing.
Good luck.

 

If i remember right the "300" designations are misfires, not injector. PO306 would be a misfire, but would probably be better diagnosed as an ignition problem. An injector throws a different code (don't have my microscan with me). You might wanna run a compression check on that cylinder. Was the o2 sensor wet with fuel or coolant?

 

The dealer said it was because of the wet weather. Just water I guess

 

so it was got water in the connector and it wasn't on the probe side of the sensor?

 

I assume so. Just got back from dealer. They seem to think water is getting in under the dash and causing some kind of control modular to send all these different codes. Also on the way to dealer the ces light went out and truck is running fine

 

Yes, the P030X is a misfire code. But that can be caused by a bad injector. They have had a rash of bad injectors in the new f-150's. they stick open at start up and get better as the engine warms up. If you pull the fuel rail off on the bank 2 side(side injector/cylinder #6 is) and put a paper towel under the injectors to catch fuel, and cycle the key to prime the fuel system you should see no leakage onto the towel. If the towl gets wet beneath any of the injectors, they are sticking open. Replace them. a leaking injector can set a rich code, due to all the fuel being dumped into the exhaust system on both the intake and exhaust strokes....

IF the injector turns out to be the problem, there is a TSB out that also pertains to changing the plug or plugs(depending on the part # you have in your engine) for this issue.

 

Just got back from cleaning truck. Guess what, it started to misfire as soon as i started it. It didnt throw any codes and after a couple of mins it ran fine. I did not spray the engine at all.Has anybody heard of what the dealer was talking about?

 

May not be related but reading this reminded me that moisture is said to be one of the culprits that causes coil failure in coil over plug set-ups.

 

But I just changed no. 6 coil two weeks ago.

 

If any coil tops have cracks in the potting material and leave mosture in or the boot seals around the cylinder head are not good, can be very suseptable ignition problems.
I have changed plugs, sealed them with dielectric grease and sealed the tops of the boots, then washed to motor off without an issue.
It's a maintaince item even though you may not think so.
Is the overall design poor? Yes, but you need to be part of the upkeep and not expect everything to stay perfect as long as you own the truck.
Once moisture gets in, it takes time and heat to drive it out.

 

But I didn't get any water near the engine.

 

Its just one of many possibilities DS, and I second the dielectric grease suggestion - very helpful. I think that even atmospheric moisture can be a problem.

 

When I changed the no,6 coil I did use dielectric grease and I live in Vancouver so its always raining. So I guess I might sell it or move to the prairies.