Originally Posted by rwenzing
Check condition and security of ground G101 - driver side near the battery, bolted to the radiator support.
Also check G103 - underhood, driver side, halfway back, bolted to the inner fender apron.
All the grounds are tight & no corrosion, but I'm going to remove all the bolts/ring terminals & sand off the connection areas again as soon as I get a chance. I even checked for corrosion in the battery terminals.
Note: I replaced all the OEM grounds and connectors with 1/0ga wire when I upgraded to a 200a alternator.
Later the same night everything went haywire, I went back out to check & everything worked perfectly. Today, the same problem as before.
Luckily, it wasn't raining, I didn't really need the interior lights or have the need for 4x4 when I had to go out of town today.
Theft light probably wouldn't keep anybody from breaking in & stealing my pack of gum out of my cup holder though.
Ford said it "might" be a bad module (I'm guessing the GEM as mentioned before) but they'd have to diagnose it at the wonderful cost of $75 per hour.