Same! That's why I'm kind of wanting to look into other used/local PCMs if I can get one for pretty cheap to try while I'm waiting for my new one... Also the wife is going out of town for a week starting tomorrow so I'm getting really antsy to have the extra shop time and want to utilize it as best I can.

I did find a guy that is willing to get rid of one for pretty cheap as he's just planning on junking the truck. He said the engine didn't have any problems running but frame/body is rotted and transmission problems. So hoping it's a good candidate..?

The part number on the PCM is pretty far off though it does come up as being for a 8.0l v10... He said the truck it came out of a was '99 Auto with 4WD. Theoretically, it should at least let the truck run, right? I believe you said other things just wouldn't work correctly until I was programmed to my VIN? What things exactly?
Can you tell things about the PCM based on the Part number? Kind of like a VIN code?

P56046359AE - My (bad) PCM
P56040157AA - used PCM

Wish I had more shop space and would take his motor too - but I've got too many 7.3l IDI and 5.0l 302 engines sitting around so the wife might kill me for that one... But she will be out of town so maybe I can convince her that I already had it..... Hahaha

 

I am really not sure what differences there would be between 98 and 99..... so far as I know, nothing changed between those two years..... Theoretically, it *should* work. Bear in mind, I am NOT 'all knowing'. So there might be something I am not aware of. (change in sensors, or whatnot.)

Generally, ABS and SRS will be upset with a vin mismatch. All that means is, you won't have ABS, or airbags.... Truck should still be driveable though.

 

Very interesting!
I'm hoping the ABS and SRS wll be the only problems. The sensors I've looked up/ordered have all said 97-02 - not to say that there aren't others that could be different.
If I wont have ABS or Airbags until I get the new PCM I'm not too worried about it. Who needs safety equipment anyways?? HAHA

We agreed on $50 and I said I'd go pull it. It's only about 20-30mins away - so I'm thinking I'll go grab it on Friday or maybe sooner depending on how things go. $50 for a working PCM seemed like a pretty good deal to me and worth the shot. I'd really like to be able to use the truck to do some work here soon so I can get to selling my F250.

 

Go for a nice drive with the wife/gf, take her out to lunch/dinner, whatever, pic up a cheap PCM. Sounds like a good road trip to me.

 

Sadly no wife+PCM pull date for me. Took her to the airport a few hours ago and just got home. Took the day off of work since I'd have to leave half-way through the day anyway and spent the morning removing all of the plow wiring (just to eliminate any variables - also want to do a better install at a later date) and going through things in the cab.

Fixed the melted/exposed headlight switch wiring - though I was trying to follow a pinout I found on the forums and a wire or two's colors weren't as the pinout said they were supposed to be... So that was interesting. Sadly, I think the switch itself is bad as well - I found another one inside the truck under the seat that also wouldn't turn on the headlights but the dimmer for the dash/cabin lights worked on. The one that was installed when I bought it didn't really dim at all just would turn the lights on and off at different stages of rolling the wheel. haha

Going through the fuse panel they had all sorts of fuses at the wrong sizes - so I got those all put back to OEM spec. Luckily I've got a big ol box of automotive fuses I bought back in the day when I was working on another project.

After a little messing with some butchered wiring I got the blower controls to work - kind of... It'll only blow on full blast - so I'm thinking we've got a blown blower motor resistor (or at least that's what it'd be in the Ford world haha). Also functions wont switch off of defrost - STRONG on the windshield with a slight breeze out of the other vents... Which from what it seems, based on the vacuum controlled actuators I saw under there, could be a whole slew of vac issues to track down.... The blend door also seemed to be froze up - but after some finagling I got it set to the heat side.

My current thinking is I'll only be using the blower when I want heat - and mainly my windshield defrosted. So if that's what it's set at for now I'd be happy. Never had a truck with AC anyway - that's what a rolled down window is for!
Maybe I'll get to fixing all of that one day....

Got a pretty interesting one I've never seen before:
I noticed is as I was pulling on wires and testing voltages - the radio would click on and off... Finally traced it down to the antenna wire - at least I think that's what it was...? There was a joint on the passenger side just behind the glovebox that when it got disturbed would make the radio pop and hum (even though it was off) and the lights on it would go out/come on. There was a shield over the connection that was loosely fitted that when I would squeeze it tight and then move the cable around the radio would stay stable... SO I put some zipties around the connection to pull everything tight and seemed to fix the issue.

Hoping to get a new headlight switch on Friday - and then be able to button up the dash the rest of the way... Coolant temp sensor, pigtail, cam position sensor should also be coming Friday and then also going to pick up that PCM. If all goes well maybe this beast will be driveable this weekend?

 

Does your truck have the cab clearance lights?

The 2nd gens were notorious for burning up headlight switches. Several companies make/sell a harness that takes the load off the switch, switch just controls a couple relays, and the relays provide power directly to the lights from the battery. (which also has the added benefit of making 'em a bit brighter) LMC truck has 'em, as does Geno's Garage. Likely other places as well. There is also a thread in the DIY/FAQ section for making your own.

 

Yeah, it does. Nothing I did seemed to make them want to turn on though. Is that an explanation for the difference in wire color?

I've read that about the switches burning up pretty easily.... I've also got a TON of relays with pigtails from the project I mentioned before. So maybe that's another fun little project I can do with this truck!

 

The clearance lights are another load on the switch, and contribute to the switch melting. I never had that problem with my 96, but, the dashboard was in perfect condition as well. Maybe it was a wednesday truck?

Need to start checking the circuit, see where you have power, and where it goes away. There are differences in the sport vs non-sport headlight setups, along with possibly daytime running lights..... If you don't have the service manual for your truck yet, download one from here. Wiring diagrams are in section 8W.

 

Hmm... So definitely need to do the relay upgrade.
I think mine has just been heavily dgaf shade-tree'd. Haha! All the wires that have just been twisted together and electrical taped I've found... yikes!

Oh nice! Those manuals are awesome! I didn't know such existed - I actually just got my haynes manual in the mail today! In addition to the temp sensor, new bulbs, new headlight switch and cam sensor. I received the crank sensor a few days ago.
Just stopped by home to let the dogs out and have a snack and then it's time to go pull that PCM!!

They called off work for tomorrow - so I'll be pulling the wheels of my wife's car and taking them to the tire shop and then it'll be shop day with the truck!

 

So I think someones opened up this PCM before - attached pictures.
Anyway - I put the new-used PCM in and got the same result. Back to the original "No 5v on MAP" code. The other two didn't pop up - and unlike in the past the truck didn't even TRY to fire.
I did some poking around and did, once again find 5v on the signal wires for the MAP, Crank and Cam sensors... I clipped the splice I had made before right next to the PCM connector and found 5V there. Then I decided I would take apart the connector itself to see if there was something going on inside that to cause any 5v shorts - and everything looked perfect.

I brought the new-old PCM inside. Hoping I can reference some electrical schematics and see if I can poke around with some continuity tests or something to see if I can identify a problem in the PCM? There's got to be a short in there, right? I mean - the guy that I got the PCM from told me the truck ran fine. There was a lot of parts gone when I got to it so I didn't get to see it myself when I pulled the PCM... Maybe he meant that it ran fine until it didnt HAHA Is this 5V short in these PCM's a common issue? Otherwise it kind of seems weird if both of these have the same problem....

After the PCM disappointment I swapped out the headlight switch and still no headlights. Get maybe a couple volts to the power pin... but the PO had tapped into the headlight wiring for the plow lights, so I'm not too surprised... On a positive note - everything OTHER than the headlights now work properly. Seemed like the lights controlled by the dimmer switch were even brighter! Definitely going to either make or order the relay harness - at a quick glance it looks like it bypasses the stock wiring almost all-together from the switch to the headlights..?

Found another kind of weird thing on accident today - when I hit my horn the hazard/turn light up on the dash...? (couldn't quite tell if they were lighting up on the truck - was too bright with the sun coming in the windows) Is that normal?