I have been following the 7.3 Threads around here for about 4 months and have learned a lot about my 2002 Work truck that I bought last year, it has always been a little hard to start when it was cool outside, but here in Southern AZ we don't get really cold, So I figured that something wasn't right.
the truck would not start one morning when it was about 45F Deg. and during my checking of the Glowplug relay I managed to short out the Glowplug relay incoming power to the PCM control connection.
Instantly a relay under the dash started to buzz when the key is on, I figured out that it is the IDM relay.

I cannot connect to the PCM with My HF scan tool that works with my wife's '03 Ford Van so I think that the PCM is Toasted.

Sorry for the Long Post but this is my time on a forum and I wanted to give as much info to help in the troubleshooting process.

My main question is; is there a reliable source for a replacement PCM? or can these thing be rebuilt if they have a burnt trace in the Circuit Board?

 

Welcome to FTE!

Have you checked all of the fuses in the fuse boxes for those that are related to the PCM and the ODBII port?

Do you have a WTS light? Does the fuel pump power up when you turn the key on?

 

In my 02 the OBDII port and cigar lighter share the #12 fuse. My cigar lighter plug shorted, which took out my ability to access the PCM with my AE.

https://www.ford-trucks.com/forums/1...e-blowing.html

Good luck!

 

What they said, check all the fuses. I am not sure if there is a fusible link in the glow plug circuit but maybe someone will chime in. The glow plug relay gets it's signal via a ground from the PCM. We are talking about a non-California model right?
What part of southern AZ are you in? Do you fabricate steel gates?

 

Good morning All, I am in Tucson, I do Some Fabrication of Gates but I specialize in Electric Gate Automation, for Gated Communities or Homes.

I have checked all related fuses, all good, I had pulled the PCM out shortly after Zapping it to inspect the board, Nothing visibly Damaged.

When I had put everything back together and reconnected the Batts, I turned the Key on and the IDM relay started buzzing loudly again, I swapped relays around with no change, any relay that landed in that spot did the same thing, which told me that the problem was elsewhere.
I have researched all over this forum and the inter-web and located a complete Factory wiring manual for my rig.
I traced the wiring and found that the IDM relay is grounded inside of the PCM, as well as the fuel pump relay, if I jumper the ground leg of the IDM relay directly to chassis ground it pulls in properly, I did not do that test with the fuel pump relay yet, but I will be looking at that soon to see if the pump then begins to work.
The fact that I sent 12V directly from the Batts down the computer controlled ground into PCM is what has me believing that I am in the market for a good used PCM, or new if absolutely needed for reliability.

Anybody have any leads?

I have looked them up on the Car-Part.com--Used Auto Parts Market website and found a few but am really gun shy of buying used electronics parts from across the country.

 

Let alone, your HF scan tool will not connect to your truck...

 

As said above, check the fuses. And is the fuel pump working when you turn on the key. That's a biggy in determining your issue. Yes goes one direction, no means a whole different story. As far a PCM goes, yes they can be rebuilt. Yes you can goto a wrecker and match the PCM number. Several models will work. Yes you can buy new. But they are like 800 bucks new if your lucky. Also, is the gp relay repaired or still broken? If broken, disconnect it, it may be back feeding the pcm telling to emergency shut down. A short will do that.

 

Just to add, its very unlikely you harmed the PCM by shorting the gp relay. It has safety features in it to prevent this although possible. I would bet you have a bad sensor or burnt fuse. There are quite a few smaller issues that can cause this. I would do some more investigation with a good scanner first.

 

Before replacing the PCM, you should make sure there is not some wiring problem causing the buzzing. You could end up frying the replacement pcm as well. The 12volts probably travelled on the pcm ground buss on it's board and then out to sensors etc connected to the pcm ground buss. The damaged components could be causing the buzzing.

 

Thanks for all of your input guys.
Right after I caused this problem, I pulled the PCM and opened it up, I could not see any fried Components but noticed a couple of dark spots in the circuit board, I then sent the computer out to ECU Repair Now in Arvada CO, Josh there said that I had toasted the Processor, they replaced that and were then able to communicate with the PCM, when I got it back and I plugged in the repaired PCM, Same Symtoms of IDM relay buzzing, I have sent the PCM back to the Shop for further Eval, I think that I cooked a Ground Trace inside of the board, I will find out for sure this week.

RetiredSparky, Good Points about the other sensors, I inspected the harness for damage on the wire that runs from the GP to PCM and all looks good.
I will probably replace all the sensors just for Insurance/Reliability.

A local friend owns a real truck shop (Semis) and when I laid out my adventures, he recommended cleaning all filters in the Fuel system, upgrading to external spin on filters to help deal with the hard start issue that sent me down this path, so I am currently working on the fuel delivery system since that is something I can work on while waiting.

 

Like Absolute says you may very well have a shorted sensor/component (he has that T-shirt). You could try disconnecting things till the buzzing stops.


If you are going thru the fuel system google "Hutch mod". It's what most of us do to the fuel system on our trucks and will ensure future reliability.

 

Thanks bigb, Good Point, at one point I had disconnected everything in the valley but was not thorough in making sure that all sensors were disconnected, I will be following up on that when I get my PCM back again.

This has been a learning experience, I knew a little about the truck since I had driven a 550 for another company when these trucks were new, and I remember that the Powerstroke would run away from the Chevy 6.5 TD trucks that were outfitted the same, that is why I wanted this truck.
But todays diesels are more like modern Gas FI cars than the old school trucks I worked on as a Fuel and Electrical systems mechanic during my Army Years.

Hutch Mod Has been completed and I am working on mounting the new spin on bases for 10 Micron filter and fuel/water separation prepump and a 3 Micron after pump filter, and I am researching a regulated return or FRx system as well to deal with the deadhead problem.

I have been taking Pics as I go and will post them in a new thread once I figure out how to do that.

 

Finally an Update on Truck Condition, I completed the Fuel Filters and the Hutch Mod, and tried again to fire it up, No Go, I traced it out to no fuel pump relay triggering, No matter what I tried the PCM refused to ground the IDM and Fuel Pump Relays.

Absolute, after your post I researched and found your Electrical Gremlins Thread and followed more links along those lines, I finally got time to go out to my shop and spend some time on the truck, I got hold of the factory wiring manual and learned how to read it, figuring out which wire goes into which plug at the back of the fuse box.
I checked Voltage at the PCM and found 12 volts at the pins that it should be at, I checked the Ground Pins and found good grounds at those pins, and 5 Volts on the VREF Pin with no changes in voltage due to sensors being plugged in or not.
My OBD port had 12 V on the pin that it should be at but after all of the checks with the 42 pin harness unplugged and all of the on cab sensors unplugged and still no Comm, I am back at the Conclusion that my PCM is still damaged even after "Repair" due to my shorting out the GP relay control lead directly to the Battery + connection on it.

Due to my lack of time to chase this problem further, I have finally given in and sent the truck to a local shop that came highly recommended, (A couple of my Business Associates have sent their fleet there for years) As soon as I have more info as to what the real problems are that caused this whole headache, I will add to this thread for others to learn from my mistakes.

 

Sounds like a headache! Sorry to hear. I hope these guys can figure it out for you!

 

Latest update, The Shop finally came to the same conclusion as me, that the PCM is at fault, they would like to send it out to their rebuilder.

I have lost faith in the current PCM due to the fact the I had already sent it out for repair and the first time it came back with the same symptoms as it had before sending it out, of a buzzing IDM relay and the second time no IDM relay buzzing and no fuel pump relay triggering at all, so I am on the hunt for a replacement PCM, the Current unit is a DPC-462, My main question is can I get any PCM and reprogram it to work or do I have to stay with the DPC-462 Family due to Wiring Harness pinout?

I also just picked up a 2000 F-250 7.3 and was wondering if I could borrow its PCM for troubleshooting? I haven't looked at its PCM to see what it's label says yet

Any Expertise or Experience on this Vehicle Computer stuff is appreciated.