'97 Explorer popping PCM MAXIfuses

[BroncoJoe19]

I guess there are a number of methiods for checking shorts.
But essentially one needs to know what items are on the circuit, and which wires are included in the circuit.
The PCM circuit includes a LOT of items.

The process, (and please if anyone with experience knows a short cut... please step in)
is to disconnect as many of the items in the circuit to eliminate them as a possible causative short, then to go through the circuit and find it.

One method is to use a test light.
check to make sure that you have current to one side of the blown fuse.

do you have a test light or voltmeter?

[BroncoJoe19]

There are almost as many circuits on each side of the PCM, and it would be helpful to disconnect the PCM and then recheck for the short. That will tell you which side of the circuit to concentrate on.

[whobub]

For those just running by this thread, please refer to my initial 'post #3' of this thread for condensed diagram/graphic of what the '97 Explorer owner's manual lists for the PowerControlModule (PCM hereafter)

So BroncoJoe--are we still talking about the PCM relay and/or the PCM maxifuse? This might also be confusing to others reading this thread--as I mentioned in earlier post there are actually two (2) references to the "PCM Power Relay". It gets a bit confusing here with the massive # of "plug-ins” to the PCM having the same name, but different components, so I wanted to take a quick moment here to clarify:

a. ONE of those references are to the maxifuse (position #2) and is labeled "PCM Power Relay"
b. The OTHER is an actual RELAY (bigger black plastic fuse-like box plugged into position #5) is ALSO labeled as "PCM Power Relay"

Again, 2 separate components--one a maxifuse, the other the actual relay.

As one can see this might be somewhat confusing if we don’t set that down right now So with that said, by ‘BroncoJoe's’ statement “The process <sic> is to disconnect as many <items> in the circuit to eliminate them as a possible short…”

BroncoJoe—so do you mean just take out all the maxifuse, relays, minifuses, et cetera???? I'm a bit confused here. . .

Yes, indeed, I do have a test light and a voltmeter. You mentioned in an earlier post that getting a 30A breaker would be better than blowing a bunch of fuses. Do you mean an actual 30A breaker as found in the home “breaker box”???? I do not have one, but could get one in a jiffy (my wife doesn’t need that dishwasher today  ). Even if I have to go to HomeDepot or Lowes to get one, it’ll be worth the $10-$20 as these maxifuses are $3 each!!!!

So let me know on that circuit breaker “tool”. I’m very interested in that angle when we get down to the final tests. Also, I can post attachments of the callout of each of the items on the PCM if you or others find that helpful/necessary.

Now I’m anxious for the “next steps”. . .

[whobub]

Checking in. . . I haven't had any time away from the "honey do" list today to make any progress. Still waiting to glance at 'BroncoJoe's' diagrams before I wander aimlessly on my own. Any others with a similar experience with this PCM/Starter Relay, etc, please feel free to chime in. Thanks in advance to all, Jesse/whobub

[Tommykim]

i have the same problem with my 1993 explorer. as soon as i turn the key on 30a fuse blown which belong to the eec power. i understand the eec fuse has everything to do with fuel pump and igniton fireing. but even though with all th relay off. still blown. any help will be appreciate or hint.

[BroncoJoe19]

Tommy,
Please start your own thread on this issue. Different fuse.
Perhaps someone will put together a how to find a short thread.

WhoBUB,
Sorry, I missed your reponse, and wondered what happened to you.

NO... what I said was the PCM!!!
Pull that. Then throw a fuse in and see if it blows.

The circuit breakers at homedepot are 110 volt. Definitely not the same.
I am not sure that using a circuit breaker is a good idea. I know I suggested it, but I was probably wrong.
You can probably use a test light, put power to the lead, and pull the blown fuse. Then tap both sides of the socket. IF the light lights, you still have a short to ground.

[BroncoJoe19]

If I miss your response, send me a PM

[whobub]

Thanks for the reply BroncoJoe. I'm not sure that this won't also be useful for those like 'Tommykim", even though he states similar cause & effect.

Sorry I didn't reply back directly to you--I'm new at this blogging thing and figured you got busy with life like the rest of us. But I think I may be onto something based on your original statements in your earlier posts, albeit I beckoned a friend of mine that has much better electrical troubleshooting skills than I since I didn't hear back directly via this forum. But all is good. . .

I was waiting to see if you had any "next steps" as you stated that you'd check some diagrams and post them, so I guess I got mixed up on what I was looking for here in the forum.

But possibly a likely cause in 'Tommykin' issues as well, I think I have found the short you suspected that it could be. And what a hassle it has been indeed--I had to take off the "plenum" (fuel injector intake manifold) to get to the wiring bundle/harness though. . . BTW--8 small gauge bolts hold this plastic plenum down to the valve head; loosen with a torx socket (I believe it was a 25 or 27 size).

See pictures--This wiring harness goes from the PCM to the rocker cover where it goes to another/separate wiring harness. I've taken some pictures and will attach them here if possible. Otherwise I'll have to do it when I'm not so tired (10:50 p.m. Sunday night PDT--yeah, I'm a wimp. . . just hope I'm making sense now ) . To make a long story as short as possible, it appears that the suspect wire is grounded to the transmission/bell housing. I say "suspect" as I have not confirmed that the wire IS shorted because I can't get my fat hand in/down far enough from up above, nor far enough UP from the attempts from below.

They are connected with the all-too-typical automotive connectors and I believe the short might have been caused from the 190,000 miles of vibration and not from heat from the exhaust manifold or the like. Until I can positively get those two harnesses disconnected (from EEC to just above transmission AND the wiring harness on the valve cover), I probably won't have any other input/guesses.

I'll close it here for now--take a look at the pictures everyone and let me know if you'd like others and I'll be happy to take them whilst I have this thing torn apart.

I hope this is helping someone. . .

Jesse/whobub

[BroncoJoe19]

Jesse,
You and your friend are doing a great job.

Tommy,
Sorry, I wasn't paying attention, I guess you are talking about the SAME fuse.

Jesse,
When I looked at the diagrams that I have, there are too many pages to post, so I wanted to eliminate half of them. The PCM is somewhat in the middle of the circuit, and so I wanted you to pull it, that way we could determine if the short is before or after the PCM.

You are already beyond that.

I'd like to mention that in the 3rd picture one can readily see where the PCM is grounded to the firewall. If that ground ever goes bad, one can get a bunch of diagnostic trouble codes that seem to be unrelated. Those codes may be along the lines of voltage lower than expected.

[whobub]

Thanks to your post and starting point suggestion BroncoJoe, I was able to at least HAVE a starting point It was up in the air as to where to start before that. In a future post I'll share a trick we used to "rig" a fuse whilst we were testing this. I was really curious about the 'circuit breaker' you had mentioned, but you cleared that up earlier--didn't make sense that a 110V breaker would trip with a 12V circuit But this trick saved a bunch of $$$ in not buying a bunch of maxifuses!!!!

Also, I'll post another picture of the "suspect area" after I can get some light to that area. Even in broad daylight that particular area is short on light for a decent non-flash picture.

My current issue now is getting the connectors disconnected. I think the age and heat have compounded the "hold" these have together. I've already snapped one of the exterior clips as the plastic was so brittle.