2012 expedition limited 120k miles. One day I was driving down the road and cruise control kick off and a large loss of power occured and the wrench light came on. Truck is still driveable just has super pathetic acceleration, but can still achieve freeway cruising speeds. When truck is restarted at a stop issues is cleared temporarily. When computer was scanned it showed a TPS code. So I replaced it, did not fix problems. Problem got worse, took it to dealer, dealer said throttle body. So I bought a throttle body from dealer did the work my self, problem still there! Then being under the hood so much I notice a pin hole leak on the rear heater unit Y hose, I ignored it because my brain was wrapped around the previous issue but the more I work under the hood the worse the leak got then it forced me to fix it! Immediately the throttle system problems went away!! This lasted 6 months of no problems. Then after replacing all of the spark plugs the issue came back with the limp mode and loss of power. Looked all over engine compartment for any kind of leak and couldn't find any. Problem is so bad that the wrench light/limp mode come on almost Immediately as soon as the engine is started,. When computer is scanned again it now says electric throttle pedal, so I replaced it, didnt fix problem! Friend/mechanic said it might be the TPS wire harness connection, replaced that too, problems still there! Please any suggestions or help would be greatly appreciated!! I am this close to trading the dam thing in but I really do like this truck so I'm try to hold back! This has been a problem for me for about a year now!!

 

We had the same "Limp mode" issues at about the same mileage. Mine spent three weeks at the dealer trying to find the problem. Ours would go into limp mode when it was raining and you accelerated hard from a stop. We did almost the same things to troubleshoot- New Throttle body; didn't help. Then they said bad Throttle body sensor: Replaced - Didn't help! 8 new Iridium plugs $100 in parts and $1,200 in labor! to extract the 5 plugs that snapped in the head ($170 per hour and they work slow...). The dealer replaced the wiring harness and did a bunch of voodoo magic (Not on the work order) and it's been fine ever since. We still have other strange electrical issues with the truck..... See Ghosts in the machine post.
our heater Y hose leaked as well / I thought it was a head gasket- patched it/ too much of a pain to replace with a new hose.Our trucks must have been behind each other on the assembly line. Looking at the new passport- no need for a 3 row SUV anymore.

 

had a similar issue with our 07Nav, even thought with issue of shifting that it might be the torque converter, but it was 2 fold 1. old clogged injectors it would go into limp mode and could clear it with code reader but would come back - and 2. the coils were failing. AND I found one plug that was backing out! those were replaced with the injectors, but after I pulled the coils and put brand new Motorcraft ones in no more hesitation on acceleration , no limp mode and no more codes. Shifts and runs, accelerates like a new truck. If you do your coils, only buy motorcraft and get all 4 on one side at a time, preferably all 8 - got mine from a dealer selling extras on e-bay , paid $25 each not the $75 the dealer wants. BTW you can rent the extractor from Autozone if you have to do this, would save you $1000 labor from dealer for something that took them a half hour to do.
Let us know what you did to figure yours out, I know you (JJdaddy56) posted in October but would like to know how it turned out.

 

The ECM will throttle back engine power if it senses an overheating condition. Have you checked your coolant level or used a scan tool to read the engine temperature as the ECM would be seeing it?

 

07 Expy 220k 5.4. Started going into limp mode and threw a tps code. Before I could buy one, it went limp on me while driving home from work and when I turned it off and started it back, I had a brand new mis-fire as well. So....I stole the TP sensor from my 05 Mustang and now I've changed the plugs, COPs, both cam sensors (just because I already had them on my shelf) did a compression test and all holes were 180ish. In the mean time I've developed an intermitten backfire through the intake. The codes were p0230, p0351, a TPS code that I didn't write down and p1000. All codes except the p0351 are gone so far but the backfire through the intake with #1 misfiring concerned me so I pulled the right side valve cover and that's where I'm at right now. And advise/help would be great.

 

Mine would go limp on the first start up of the morning sometimes so I don't think it woukd be due to temp but any other ideas would help.

 

What wirring harness did you replace?

 

Sounds similar to my wife's 2014, I don't remember all of the symptoms or if there were codes or what they were, but ours required the transmission lead frame replacement. Been a year or so with no issues.