Got an issue with my 2005 f150.

Basically if you turn the heater on level 3, it knocks out the radio. Turn headlights on and it will knock out the heater. Everything turns on the 4 way dash lights ( not actual exterior lights) and everything knocks out the brake pedal so I can't take it out of park, although brake lights work.

Kicker is, I hook up my scanner and truck works as designs. Unhook it and it goes tits up.



My friends dad is a master mechanic for Ford and he's even stumped, so I don't feel so bad.

He doesn't think it's the computer but something isn't letting the systems communicate but the scanner is forcing it to.

He's gonna do some research tomorrow and get back with me on how I should proceed

I hate electrical....

Just leave the scanner hooked up…. It sounds like the ‘brain’ is fried.

That was my first thought about the PCM, my friends dad doesn't think so but it's not ruled out.

He said that 2015's have been know to do this and it was the fuse box. He has to look into the 2005's.

If I was driving it, scanner hooked up and im golden but the wife drives it alot so I wanna fix it.

Hook up a scanner and monitor BCM while prompting commands.
Toggle commands through BCM, monitor output.
Sounds like possible BCM, Have seen stranger things happen.
Just for S&G, smack the top of dash while running, see if any changes.
Have replaced instrument clusters for similar problems.
Ask your Ford mechanic to look for TSBs concerning same.

Nothing worse than electrical issues, unless you're one of those strange people who really likes electrical issues.
I'm fighting some myself on a Frankenstein Jeep I kind of sorta inherited. Getting close to ripping out the whole system and rewiring the whole thing.

Back in my Youth, 1960's' if my 57 Chevy didn't run, it was fuel or electric. Both were easy to sort out. Now you need a fortune in equip. to sort it out & a supply system to send parts that might help. BACK IN THE DAY, I wrenched on B-52's. They had miles & miles of wiring & lots & lots of systems, but you didn't need a FACTORY COMPUTER to tell you how to make it (the aircraft) work. Friends, we are screwed !!!!!

I had this problem with a 2003 F250 Super Duty. Like the radio would stop working and at the same time the drivers window would not go up or down! Yea, crazy stuff. The problem was the solder on the dash circute board was comming loose. Replacing with a new OEM from the factory would sooner or later give up the same problem.

I took the dash apart "see youtube" and sent the entire board to some guys in one of those southern states. They did a very good job and have not had any problems since.

BTW this took a LOT of internet research. I might still have address etc.

https://circuitboardmedics.com/car-truck-instrument-cluster-repair/

So today I cleaned 6 grounds that I could find under the hood. Kinda corroded but seen worse. Now the truck won't start....should have left the corrosion

Did I say I hate electrical problems?

Did you unhook the battery before cleaning those grounds?

Did any of those spark pretty good when you went to reattach them?

No sparks. But when hooked up positive battery cable, the headlights flashed.

Joel,
Pull engine/trans/transfer case, to get good access.

Replace wiring harness. No easy way out,you have wiring harness damage and it probably damage the computer. Send computer out to be tested.

Other option, find a simple early ford or chevy truck.

With the soul-sucking bs you're dealing with, an old Ford with a 300 inline six will bring you a smile everyday you work it, or work on it:

An idea I'm pondering. Those little 300's are bulletproof and actually can make decent power. I got a lot of past time working and using them. Used to be able to buy a kit for fuel injection for around $800 to get rid of the carb if I can find a clean older truck.

I bet some of those old trucks are in great shape down your way.

Beware of some of those cheap fuel injection kits. Bunch of Chinese garbage in both the holley sniper and fi tech.

Only one I'd ever consider is howell tbi. They do a very good job and use only quality stuff:

https://howellefi.com/product/hf300-ford-300-cid-tbi-conversion-kit/

Anyhow, it's hard to beat a motorcraft/autolite 2100 2-barrel carb and a simple air/fuel gage for tuning.

They have something like 12 tiny little annular boosters. Excellent fuel atomization at low speed or idle. Super easy to tune and they work well off road.

No man should be afraid of a nice truck carburetor. Autoline in Winnipeg manitoba builds all my firewood truck carbs

Actually trucks down here rust out real fast due to the salt in the winter time they use for the roads.

When we moved here in 2013 from AK, we brought back a really clean '96 Z71, within I'd say 3 years, cab was going to shidt.

I really like those 300's. When I worked at ANC international, most of tugs had those things. Had to eventually install the FI upgrade kits and get rid of the old 1 bbl carb. Rampers did not know how to work the choke. Then after they flooded it, they figured they could fix. I got sick and tired messing with carbs in the middle of January cuz of stupidity.

Sounds like a ground problem, and now it sounds like more problems after cleaning grounds

The best thing they ever did to the 300 inline six was add fuel injection to it. Night and day difference. The old carbed model was a gas guzzler and lacked power. Going back to a carb set up would be a straight up step backwards. The engine itself is bullet proof as can be, but don't limit yourself with a damn carb..

A well tuned carb doesn't limit an engine's horsepower bsa.

Plenty of healthy, 275-300 hp for 300 fords and 292 chevys out there, with carbs.

The efi 300 ford was a great engine, it was more than just fuel injection. The 2 piece cast exauhst manifolds were the best.

May as well been called cast shorty headers.

To improve fuel economy on the inline 6's I've found that staying with a low end torque cam helps.

Decreasing internal friction helps.

Shaving the head and decking the block to bump compression

And if a carb, tuning with an air/fuel gauge as well.


Decreasing friction:
New low friction rings. The 3.5 ecoboost takes advantage of low friction ring technology.

Roller cams

Roller rockers.

Highway friendly diff gears

Avoiding excessive suspension lifts

Thinner viscosity gear oil

Electric radiator fans.

Keeping a truck that is shaped like a brick, under 65 mph.

I don't daily drive a truck, they're only used for hauling and towing.

Check out this conversation with an expert from Total Seal. Learned sht I never knew!

Ford's 300 was developed from a 240. The only difference was the stroke. IIRC, all the parts were interchangeable except the rods. The 240 was as reliable as the 300 would be but just had a little less torque. Once the 300 came out, the 240 disappeared quickly. I had a '68 F100 with a 240 and it was highly reliable. I didn't do a thing with it in 100k miles. If it had been a 4x4, I would have swapped the engine for a 300 and would still be driving it.