So I was parked at a gas station, went to start the Expy, and heard the familiar buzzing sound from the previous time. Checked the PCM relay, and it was burnt in the same spot, prong number 5.

It was 8:30 on a Sunday afternoon, so none of the auto parts stores were open. Got desperate, opened the relay up. Seems it's a normally closed relay that opens when the key is turned into the on position. At least the engine started when held the 2 contacts apart.

To make a long story short, I ended up looking at the manual for anything with a relay that I didn't use. Used the trailer wiring relay. The diagram and size matched the burnt one, so I stuck it in there. After a 2 hour drive, the relay was rather warm to the touch, almost hot.

So I guess my questions would be: What would cause the PCM relay to burn out? How warm is normal for these relays to get?

Some info: 2003 Expedition, 4.6 engine. Last time the relay burnt was at least a couple months ago (I posted a thread on here, lemme see if I can find it.) I'll post what goes to the relay tomorrow, when I look at the manual, as well as a picture of the burnt relay and it's diagram. I don't know if it's coincidence, but it rained today (like last time.)

Here's the previous time it happened, at least 6 months ago. Click Me

Found what's controlled/connected by the relay: Fuel Pump relay, fuel pump, PCM solenoids and sensors, fuse 32 (Catalyst Motor Sensor, transmission solenoids), fuse 33 (Canister vent solenoid, HEGO sensor, VMH solenoid, Intake Manifold Tuning Valve solenoid, A/C compressor clutch relay coil, EGR vacuum regulator solenoid), fuse 34 (PCM, fuel injectors, fuel pump relay, fuel pump shutoff switch, fuel pump motor, idle air control solenoid, MAF sensor.)

Sorry for the long read, but I'm trying to be as thorough as possible. TIA