symptoms:

1) Wife has been noticing Low Fuel light rapidly cycling on and off a couple of times in the last week even though there is plenty of fuel<O></O>

2) wife was in reverse yesterday and noticed back-up sensor alarm going off when her path in reverse was clear<O></O>

3) went out late tonight to get something out of the truck, open back doors and interior lights started to blink rapidly and I could hear the relay rapidly switching on and off. Placed key in ignition and all instrument panel lights were very dim as if the batteries were bad and could still hear relay rapidly cycling and interior lights were also very dim. Happened to push in Emergency Blinkers on and off and BINGO, PROBLEM WENT AWAY – the lights brightened, relayed stopped cycling, was able to start and test drive with no problems.<O></O>


Anyone have any idea what could have caused this? I’d like to fix the problem now before my wife and four kids get stranded in this vehicle. <O></O>


Thanks

jmfcst@yahoo.com

 

could be a short in the wire harness going up the steering column...the wires some time chaff and short out..

 

This sounds like a loose/corroded ground on the GEM or PCM to me. The additional current draw of the flashers temporarly bridged the poor connection.
I would begin by looking for any evidence of windsheild leakage above the dash fuse panel or around the PCM. There has been a few GEM replacements that were caused by the fuse box/GEM location and leaky windshields in the pre-2002 PSD's.

 

ok, thanks, until I get home tonight and check that, let me give up a little info on my engine cleaning habits and maybe you can tell me if I might be the cause of the problem...

About twice a year, I take the truck to a self-service high pressure car wash and while the engine is running I use about 2 cans of degreaser and then wash the engine with the high pressure washer.

The last time I did this was in mid Dec 2006, about a month ago.

Is this good practice and could the high pressure have caused "windshield leakage" to cause the corrosion you mentioned?

Also, where are the grounds for the GEM and PCM located?

 

High Pressure wash is never a good practice under the hood. Too many connectors that can get infiltrated by water and cause your corrosion problem. With that, I would forget the GEM and PCM for now and start pulling underhood connectors apart with some high quality spray contact cleaner. You should also get some dielectric grease when putting the plugs back together.

Pull each plug apart and look for corrosion. If found you will want to attempt to remove with a small tool and spray with the contact cleaner. Spay each plug with contact cleaner if corrosion is found or not. Place a small amount of dielectic grease around the outside of the connector before reassembling, not on the pins. The grease is to keep additional moisture out of the connectors.

Search on simple green and engine cleaning to see the proper way to clean your engine bay.

 

ok, thanks><O></O>

where under the hood of my 2000 7.3L diesel should I start? which connection is the likely candidate affecting interior lights, backup sensors, fuel light, relay, emergency flashers, ignition...<O></O>

<O></O>

...with all these systems sharing a common short, sounds like the immediate system-wide problem is linked to a single failure involving one connection. but which connections are the most likely candidates? is there a way I can do a targeted search instead of blindly checking each and every electrical connection under the hood? (I am technical but currently familiar with only the very high level details of my Excursion's electrical system) <O></O>

<O></O>

thanks again<O></O>

 

actually, since I could hear a relay cycling rapidly (which I am assuming was the cause of the lights blinking rapidly in harmony with the relay), it seems that the relay is in series with the short, no?

 

Elecrical gremlins of the sort that you are dealing with are not fun to find and usually take an enormous amount of effort.

You have probably noticed the large quantity of plugs along with the fuse panel located under the brake cylinder. This area will most likely be the source of the problems. There is one large plug that goes through the firewall there will a jillion wires to it, that's the one that plugs into your PCM... the main computer that controls just about everything. Most of the other plugs under there also connect the engine and fuse box wires that connect to the PCM plug or main wiring harness that goes into the cab and runs all that stuff.

I wish I could point you to one of them that is more suspicious than another, but I can't since a poor connection in one area can affect another. With the underhood fuse box, you may want to check for corrosion on the various fuses that control the relays and lights that are immediately giving you problems, sometimes simply removing and re-inserting will scratch off any offending corosion.

 

Ok, problem has happened again twice this week (rapid relay switching, all electrical systems not working, problem corrects with turning on bunch of stuff on like windows/doorlocks/wipers/flashers/etc, but that trick didn't work this last time and it is dead sitting in my driveway).


I took off and checked the two top plugs under the break cylinder and they looked great, no corrosion


I checked several other connectors under hood and everything looked pristine.


Also, I pulled passenger-side interior fuse box with connected GEM and everything looked great. No sign of corrosion or damp carpet or any other signs of water seepage.<O</O

 

PROBLEM FOUND AND FIXED...battery terminals needed cleaning!

I am embarrassed but thankful!

 

I was just dealing with this EXACT same problem. I had extras so I replaced the relays and no change. I was starting to think it was the GEM. I did a search, and found this post. I went out and cleaned my cables, and she is 100% again. I am just a little embarrassed about it as well.

Just another reason I love this site!!! Booh-YAY!!