First post, let me know if I messed something up.

Hi everyone. I bought a used 2007 F150 4.6L Triton, 175,000 miles, have driven about 600 miles. I’m having several problems and I don’t know enough; I’m hoping you can help me draw a connection between them. I’ll list them.

Has blown fuse 14 twice in 600 miles Last time was two days ago.
Has blown fuse 102 once in 600 miles. Today.
So 3 total blown fuses in 600 miles.
The CHT pigtail wire was cut in half (rodents? Caught in serpentine belt? Touched something and melted apart?) I replaced it and that has worked fine. The latest two blown fuses (listed above) happened directly after this repair.
Has a grinding noise from front driver side on acceleration or when turning right, only under load, not in park. (Combing forum has led me to believe this is IWE system related, but I haven’t had a chance to try a fix yet yet because fuse 102 blew, so this electrical problem took priority.)

I don’t know if it’s worth noting, but every problem EXCEPT the first blown fuse 14 has happened within 3 days of driving after the truck sat for one month. For example, the truck wasn’t making a grinding noise. Then it sat for one month. And then it was suddenly grinding first drive after the month sit.

I’m pretty inexperienced at car work, so I’m just listing all that in case someone sees a connection between them. Mostly I’m wondering if there is something that would cause fuse 14 AND 102 to blow. Transmission range sensor, maybe? Seems like a different fuse will blow tomorrow.

I can’t quite wrap my head around the wiring diagrams yet. Trying to learn how to use a multimeter to “test grounds” but I need to learn what that means.

Just wondering if someone might have any suggestions on where to look/connections to make. Thank you guys in advance for any help you can offer.

 

Wire harness with missing insulation (or black protective stuff), resting on the….engine?….wit oil on it

The photo is looking behind the passenger wheel well.

Hi again everyone. I’ve been continuing to look into this today. I found this wire harness. Am I right in saying this could be causing a short? It’s the cluster connector on the PCM that’s closest to the driver side.

I’ve tried to find the “pin out” diagram, I think it’s called, to see if Fuse 14 and 102 are served by this cluster, but I can’t find mine specifically—2007 4.6L 4x4 STX.

Is there anything about the IWE system that could be messing up due to this cluster of wires shorting out?

 

I can't tell from your photo if that wire harness is shorting out against something or not, but if it is then that's 100% where you need to start. Repair/insulate so the wires are protected and not shorting into each other or onto the motor.

Fuse 14 typically blows if the pcv heater is shorted out but that's the only common cause I've read of.

Fuse 102 goes to the ignition switch and then from there it splits into lots of other fuses/switched circuits and 14 is one of them. 102 is a 20 amp and 14 should be a 10 amp, but conceivably the could blow at the same time if someone replaced f14 with a 20 amp fuse, or if like you show those wires were grounding out and they are powered by those fuses.

 

Thank you so much for your response! Ok, that’s where I’ll start asap. If my understanding is correct, these wires could look like that in the photo and be touching the motor, but if they aren’t damaged—don’t have exposed copper—then they’re not the culprit of the blowing fuses. And just so I’m clear, am I supposed to visually inspect each wire in the cluster and then test each wire with a multimeter to make sure it’s working properly? Or is a visual inspection sufficient—look for bare/frayed wire and replace the ones that look damaged?

Fuse 14 was replaced properly with a 10 amp, so we know that wasn’t the problem. Timeline was this: truck sits for a month; Day 1 after month sit (and each day thereafter) shows acceleration grinding problem; Day 2 visually inspect for grinding problem and find CHT connector pigtail severed, replace, later that day Fuse 14 blows; Day 3 Fuse 102 blows.

Yes I read about the PCV thing. Oh, interestingly, we read about that on Day 2 while fixing Fuse 14, unplugged the PCV heater wire per someone’s suggestion on here, and Day 3 we blow fuse 102. We unplugged the PCV without disconnecting the battery…maybe that was bad.

So many thoughts. Anyway thank you again for sharing your time and knowledge with me, I really appreciate it.

 

I don't know what all runs through the harness in question without researching, but yeah if the wire insulation isn't chaffed through to where they are shorting onto metal or into each other I would look elsewhere for the problem for now.
as to the hub grinding, a stab in the dark but maybe a rodent chewed through one of the vacuum hoses if they've been chewing on wires?
It's pretty simple to visually check the hoses for holes or being disconnected and /or get a vacuum gauge and check to see if they hold vacuum.
"Fordtechmakuloco' on YouTube has a lot of videos on troubleshooting things like the IWE on these trucks.
"Chrisfix" has lots of videos in general like how to use a multimeter I'd guess for vehicle. You would have to unplug both ends of that harness and check resistance/continuity by probing both ends in ohm/continuity check mode.

 

Sounds great, I’ll check those YouTube recommendations out, I appreciate it. We’re currently watching Eric the Car Guy explain how to diagnose electrical problems.

Yeah, that’s a fair stab in the dark about the vacuum hoses. I’ve read a ton about the IWE system in the last couple days, including the awesome sticky how-to post on here for diagnosing trouble with it, I just haven’t gotten to it because when fuse 102 blew, the car wouldn’t start at all, and so the threat of that happening again took top priority. Then when I realized these blown fuses might be related (by a short in a cluster of wires), I was just hoping maybe there’s an electrical component of the IWE that could be served by that same cluster of wires….just hoping all our problems are related! Fat chance! : )

Anyway, thanks again. I’ll keep plugging away at it, and if I discover anything helpful, I’ll report back. And if anybody out there knows the magical connection between these fuses and the IWE grind, or if there’s something else I should be thinking about here, please let me know. Oh, and if anyone happens to have wiring diagrams or ping out diagrams for a 2007 4.6L 4x4 STX, I’d be very grateful! I can’t seem to find those (except the ones in the Haynes manual).

 

http://WIRING DIAGRAMS - DeVoll http...searchable.PDF

This link is what I use, it's a 2005 diagram but probably 99% of stuff is the same from 2004-2008 but there are some minor differences, so don't hold this as an absolute.

 

Just trying to update as I do this work. I was finally able to get the passenger front wheel off & get under the truck and inspect the wire harness I showed in the initial photo. This wire harness was sitting ON the engine, covered in oil from the oil leak, and there was exposed copper on the two wires of that wire harness/cluster, which seemed to have been caused by friction/pinching because those two were pressed against the (sharp!) corner of the engine. I used electrical tape to tape the individual wires that had exposed copper. Then I used electrical tape to tape the cluster where the loom had come off. Then I zip-tied the cluster to some other hoses above it to try to lift & hold it off the engine….i didn’t know how else to get it off the engine.

I also found two more spots of exposed copper on wires (weirdly part of the same cluster) over on the driver side where they were plugged into something on the transmission. Because these were so hard to reach, I used liquid electrical tape on those spots to cover the torn insulation. No idea how those got torn…maybe a mouse.

So far no more blown fuses.

But now the truck has a very noticeable shudder, especially at idle. And a loss of power. This has to be connected to the work I did or it’s the biggest coincidence ever. No idea what happened. I’ve posted another post asking for an under the hood anatomy resource so I can start to try to guess what went wrong in my repair. Wondering if I pinched a wire by zip tieing that cluster up off the engine, maybe.

will update more as I can. Super frustrating.

 

Oh, forgot to mention. This wire cluster is plugged into the PCM, and it’s the farthest cluster to the right (closest to the driver side) on the PCM.