ECM issues with 2010 Ford F-150?

I've seen ecm issues where the key won't connect or you're put into limp mode, but I've never seen anything like this before.

After sitting for about a week I cranked the truck up and as I was driving off I noticed a thermometer looking warning figure.  It seemed to work alright and while it was a cool morning it wasn't even below freezing.  I drove it for about 40 miles and everything still appeared to work but the emblem never went away.  I presumed the engine temp sensor must have gone out or the wire had fallen off the sensor.

I forgot about the issue when I got home and 2 days later when I went to drive it again the emblem appeared again so I went to an O'Reilly's to have the code read.  On the way I decided to get some gas and almost immediately I got a "check fuel filler" notice.  Since the Ford doesn't have a gas cap I just stopped at the next filling station and inserted and removed a gas pump several times thinking that possibly it just hadn't sealed well, but it didn't fix that problem.

When I got to the auto parts store and they read the codes they said the head temp sensor (underneath the manifold) was out plus it showed that it had been overheated (no it hadn't!!) and that the fuel filler just wasn't sealing properly.  They could remove the fuel filler code but couldn't remove the temp sensor code naturally.  They sent me to a local shop to have them look at it because while l have no problem replacing the normal temp sensor on the block I simply don't remove intake manifolds anymore unless it's for fun or RACECAR.

He read the codes and said that it wasn't the sensor, it actually was a RAM read error and he referred me to an auto electronics shop.  Apparently throwing random codes is a sign of a bad ecm.

it also has some sore of subroutine that says if the sensor is out and it doesn't know if the engine is cold or hot to treat it as if it's both so the fan just roars at full speed plus it's running rich as if the choke circuit is on.

I called the shop to get some idea of whether this was something they could repair codewise or if it would need a new computer and they seemed to say I would need to just replace the computer for a cost of about $800 for a used one.

So now my question to the collective is this simply replacing the main ecm or are there other computers in the F-150?  And why wouldn't I go buy one from a wrecking yard and replace it myself?  Is there programming that needs to be done after I replace one on the truck?  How about key codes?  I had to have Honda redo my key codes on my S2000 when I replaced one many years ago.

First, id be skeptical of their diagnosis. Especially since some of it was over the phone. It is not uncommon for the CHT sensor (and it's wiring) to go bad. Nor is it uncommon for the cap less filler neck, or other parts of the vapor management system to fail. Take it somewhere (not Oreillys) for proper diagnosis. 
To the rest of your question, no you can not just buy a used one and throw it in there yourself. Yes it only has one PCM, but it has to be programmed with the PATS key info along with other module configurations. 

I did take it to a "professional" to get the diagnosis.  The only phone part was to see what cost might be.

So if I replace the ECM myself how do I get it to the Ford dealer to have the PATS key programmed and what do you mean other module configurations?

Checked with a tech at work- it's much more likely to be a sensor or wiring problem than an ECM problem.   Since that would carry over to the new ECU anyway- that should be checked first.  Given how the sensor works, the highest odds would be a wiring problem- which would most likely be a chafed hole causing a short.

Fundamentally someone needs to go in there and put some test equipment on the wires to measure the output of the sensor at the sensor end of the wire and at the ECU end of the wire.  That tells you if it's the sensor, the wire, or the ECU that's bad.  Throwing a new ECU and a new sensor into it will also tell you that, but if it turns out to be a bad wire then it will have cost a lot more money to do it that way.  Replacing the most expensive part first just because it's easy is usually not the right idea, at least not unless you've already got a known-good spare sitting around.

carguy123 said:

So if I replace the ECM myself how do I get it to the Ford dealer to have the PATS key programmed?

Have it towed.

I'd definitely be testing things like the voltage at the sensor before throwing a PCM/tow bill/dealer reprogramming at it.

In reply to STM317 :

The sensor shows input too high, which is supposedly confirmation it's the ecm.

And yeah I'm concerned enough about the cost to want to look at alternatives.

In reply to carguy123 :

I'm assuming this is a 5.4L? What specific codes are there?

A basic OBDII scan isn't proper diagnosis, it only points to an area that needs further investigation. I'm saying that the  cost of PCM replacement/reprogramming means it's worth actually getting hands on the sensor, disconnecting the harness from the sensor, and checking the voltage supplied to the sensor.

- IF voltage is indeed too high as the fault code indicates, then it may be a PCM issue, or a wiring harness issue (would need further diagnosing).

- IF the voltage supplied to the sensor is proper, then it's likely just a sensor issue that can be solved for much less money than replacing the PCM.

The thing about just using the parts cannon in this case is that the new PCM may not fix the issue if it is actually the sensor. And you won't know until you've spent hundreds of dollars to get the replacement PCM working. So you'd pay a bunch and deal with a bunch of hassle having the PATS reprogrammed only to find out that you could've just replaced the sensor or repaired the wiring harness for much less.

Actually replacing the sensor isn't that much less expensive than replacing the PCM and the $800ish includes all the programming needed.

And the engine is the 4.6