GRRRRRRrrrrrrrrr...PCM fuse keeps blowing!
 

...and I unplugged the fuel bowl heater!

The Ex left my wife on the side of the road last night and I had to have it brought home on a flatbed.

I checked the F5 chip at the PCM and it's still secured and sealed by the duct tape and it's still firmly connected to the digital switcher.

I SUCK and anything electrical (my mind just doesn't grasp the basics of wiring etc), so if anyone has an idea on what to check, especially if it involves using a multi-meter, please explain like you're talking to a 15 year old. When I read where someone say's to Ohm something out, it's like they're speaking in a foreign language. :o

Stewart

So it blows #30 fuse when you turn the key to the KOEO position?

The second you turn the key on, it blows. (I'm at Stewart's right now)

isn't that the same one that the fuel bowl heater is on?

oops.... did'nt read close enough

Peter,
Try unplugging the wastegate solenoid and try changing out the pcm relay. And also check for chafed wires,

I had this exact same problem a couple years ago, all the way down to "unplugged the fuel bowl heater and no change"

My culprit was a worn spot on the wiring harness atop the DS VC. In my searches I also checked the DS shock tower and the OD wiring at the steering column. Mine was the VC though. Went through a lot of fuses, and ended up needing about 10" of electrical tape.

This is exactly what I pm'd Stewart a few hours ago...

Stewart, I'm like you when it comes to wiring. I need it written down so I can look at it to know what i'm doing. Thats what I get for being in the AF and working on airplanes. We have a book and it tells you exactly what to do and it comes with pictures.

Great minds think alike!

Will try that tomorrow, thanks!

The drivers side harness atop the valve cover is good to go, no chaffing. (2/1/13 edit to add: To be more specific, the wires on the outside of the valve cover leading to the 42-pin connector was good. I hadn't yet checked the wires on the valley side of the engine)

I didn't think the OD wiring in the steering column could do this, but I'll check it tomorrow too. Already had to replace the one in my old F250 when the OD button quit working.

I know this fuse is for the PCM, the wastegate, and the IDM. Hopefully it'll be something easy.

Stewart

Darnit, was hoping you'd catch a break there.

Good idea unplugging the wastegate, hopefully that does the trick.

As mentioned above, the only things on Fuse 30 are the wastgate control solenoid, the fuel bowl heater, and the two relays that enable the engine to run - the PCM power relay's coil, and the IDM power relay's coil.

The last two are fed through the PCM Diode in the front of the under-hood fuse and relay box. That's the little black thing in the extreme lower right in this photo (ignore "here" and arrow), and unplugs the same as anything else in that box. Be careful, though, it has to go back in the same way it came out, (but it can only fit one way). BTW, the other thing right beside it is a diode for the A/C clutch.

If you remove that little gizmo, the truck definitely won't start, but you will have eliminated half of the things that may be the cause of the short.

If the fuse no longer blows, then it's one of the two relay's coils shorted. Those two relays are identified as the arrowed "here" (the IDM), and the relay that's two above it at the top of the stack (the PCM relay). Pull them out one at a time and see if the short goes away.

If it continues to blow, it has to be either the wastegate solenoid, the bowl heater, or the wire thereto. The current gets from the relay box to those items via a cable that goes through the valve-cover 42-pin connector. Pull that loose and see if the fuse still blows.

If it keeps blowing with the 42-pin disconnected, it's somewhere between the fuse box and the 42-pin connector. Someone mentioned chafing along-side the shock tower.

If not, the short is in the engine valley's wiring somewhere. Since you've already pulled the heater loose, pull the wastegate control solenoid and see.

If you need the wire color (RED/LT GRN), here's a diagram:
http://springerpop.net/F350/PDFs/Eng..._controls1.pdf
It passes through the 42-pin connector on Pin 35.

Pop

No picture?

Stewart

Wow, instant picture, LOL!

Stewart

Excellent!

Thanks!

Stewart