Hey guys. I have a 2005 5.4 3V that got water in the PCM, causing a misfire code on cyl 7. A new coil did not fix it, but a test light showed the output from the PCM blinks just 3 or 4 times on startup, and then quits. Before I go buy another PCM, I thought I'd pull this one apart and look to see if there are any deposits/corrosion from the water on the circuit board. I removed the 7 torx screws on the PCM box, but nothing is coming apart. What's the trick or full-moon incantation to getting this separated?

 

My guess is whoever manufactures that part for Ford doesn't want it separated or "user serviced". Mostly likely you'll find its been "potted" which makes it a chunk of PCB and components encased in epoxy.

Even though there are screws holding the case together they might be part of the original manufacture or assembly process.

Please let us know if you find something interesting in this-------I myself would just buy a known good (or fully warrantied) replacement PCM.

 

I would normally agree with you, but there are services that repair your unit and return it to you, like this one:

04 10 Ford F150 ECM ECU PCM Engine Computer Repair Return Ford F150 ECM Repair | eBay

This would imply that the case comes apart and the board is serviceable. In addition, a potted board should not gotten damaged from water incursion. "Should" being the operative word.

In my previous career I had a customer come back in complaining about sporadic car alarm misbehavior. Turns out the windshield was replaced with a bad seal job, and every time the customer washed his car some water leaked down the wiring harness for the alarm under the dash. There was notable calcium deposit on the circuit board. Calcium has 40% of the electrical conductivity of copper, which is more than enough to create shorts in this application. I hit that board with the proper cleaner and the customer's problems went away. Except, of course, for persuading the glass company to reseal the windshield.

So, there is the reasoning for my attempt to fix this myself. The fact that the coil feed blips on start crank, and there is no misfire under full throttle, "hints" to me that there is perhaps more voltage or a longer pulse during those situations. This would be indicative of a partial short rather than a complete component failure. This is my speculation and nothing more.

I have read several posts from truck owners that have gotten their PCM's wet and experienced problems. I was hoping to maybe find a DIY cure for some of us. If I can't get this thing apart I guess I'll just send it out. There apparently have been updates to the original software which my unit does not have, so at least I can get an update included in the cost of repair.

 

Hey there--I'm in that biz so look out! But you're 100% correct---windshield leaks after replacement can be an issue, good glass shops take care of the problem without hesitation. Of course by "good glass shop" I DO NOT mean SafeLite! Here locally in the trade they're known as "LeakLite".

Your reasoning on the ECM potential failure is pretty much spot on----and thanks for alerting me and others a rehab service does exist for those.

Hope your's is an easy fix----and cheap too.

 

Hey did you ever figure out how to open it? I have a 2004 F150 5.4 3v, and I believe my PCM is bad, so I wanted to open it and see if I can notice any damage. But I ran into the same problem after removing the 7 torx screws and it wouldn't open up!

 

it has adhesive to seal it from water you have to pry, and it will open up like an alligator, and then the middle metal part pulls out

 

it has adhesive to seal it from water you have to pry, and it will open up like an alligator, and then the middle metal part pulls out