PCM failure? How tested? code 543

How can I test my pcm on my 95 3.8? :runaround: I'm afraid I fried it as I had put in another thread about "fries, codes 543..., (link at bottom)" :headshake :crying: I'm listing this again, because I was hoping to pickup someone who knows about testing the pcm. The 543 remains after clearing and retesting. Car runs decent at start up, but becomes rougher as it warms up. At idle, it runs like someone is lightly tapping the pedal, somewhat like it is trying to keep from dipping to too low an rpm. It sounds better at a higher rpm, but it really isn't and it acts like it will stall once returned to idle. I checked fuel pressure and it seems ok and consistent with measurements on another 3.8. I also checked the engine temp circuit that I think is where I fried the pcm. When pulling the connector from the temp sensor, the rad fan came on as it should and the fans came on as they should with a typical engine warm up and they cycled on and off as expected. This makes me wonder if the pcm is really bad. With the rough, rich running, something is not right. :screwy: Any help would be GREATLY appreciated!!! Thanks a lot!!!

http://www.automotiveforums.com/vbulletin/showthread.php?t=897392

Any chance you knocked the intake air tubing off when dinking around with the ECT sensor wiring, or maybe knocked and cracked a vacuum hose? Where is the ECT located on your '95? Is it near the IAC or the DPFE by chance? Kind of sounds like what you could expect from a vacuum leak.

I'd suggest taking another look under the hood, even in areas you don't think you were experimenting with. There is an off chance the timing is just coincidence. If you don't find anything, hand a friend a bright light and ask them to look around.

Since you're getting codes out and the cooling fans seem to function properly, you're probably not looking at a fried PCM.

-Rod

Wouldn't all of that be nice. Like I said before, I could smell something got really hot and burned and strongest inside. Knowing what I had done and what happened when I did it, I followed my nose and gut and punny brain to the PCM as I had always suspected, and sadly it was victimized. :crying: :crying: :banghead: :banghead: :bricks1: .

Actually, I may be able to recover it, but it sure would be nice to have the schematic to it to be sure I reconnect things correctly. I say that, but this thing has three or four layers to the pcb, like I'll be able to sort things out, and I think Ford and the manufacturer, Motorola, probably don't want their proprietary info out, though the schematic still could be helpful. I burned a small hole where there were no components, just a juncture point. It actually has 30g or so copper wires embedded in it that melted. I'm hoping that if I figure out how many of these wires should go to the solder node at the burn site, I can put a bead of solder to join everyone back up.

I have a 94 taurus with the 3.0 engine that I could borrow the PCM and try on my 95 and see if everything else is ok, or does that sound too risky? And if so, how do I verify that everything else is ok when I do put in a functional PCM? Everything else seemed to be working properly, ccrm, icm, fuel systems, no other codes that would suggest that something else is not working properly, that I would be concerned adversely affecting the pcm.

Rod, can the PCM schematic be found? I didn't think it was in the TSP, because it's not broken down in the electrical section, and the diagnosis section just says to replace it, not repair it, implying Ford service doesn't have any reason to have or need such diagram, and I imagine not skilled to that either.

If I have to, any specific suggestions as to where to get one at a descent price and what to expect to pay?
Thanks

Hmmm, that's a bummer. How close to an output pin is the burned area? Can you follow a trace from that spot to the multipin connector through vias and whatever else to determine which terminal it connects to (Keep in mind that you may need to scrape away post coating to get a good continuity reading)? If so, cross that pin to the wiring diagram in the service manual to see if that correlates to the ECT connection. If it goes elsewhere, then you have some more digging to do before connecting another or repaired PCM to the car.

I've never managed to stumble across a schematic for the PCM. Is the hole where there used to be a component? You have my e-mail address, any chance you could send me a pic of the damage? I might actually still have a PCM from my '94 Taurus SHO that I could try to compare this against....or reverse engineer.

-Rod