Ωhm

Don't know my plugs as good as I should. Maybe someone else can chime in.

Seems like a vacuum leak somewhere. Bad/fouled plugs can cause lost of vacuum. What kind of plugs are you running with?

Looking closer at C103 photo, wire colors don't line up. Seem to be C105 (Engine to Alternator), same as C103. Buried under that connector in photo is there another 6 pin connector?

One on your thumb is 4W/D switch, on your fingers is Cruise Control ground. Man, I was hoping by now you would have found something. I just know D1_5 (HOT at all times) should not have continuity to D2_4 (SW IGN I1 feed). Not sure about Red or Yellow wires going to C101.

Bottom photo: Electrical Cooling Fan Top photo: Keep in mind the Relay Blocks can be assembled many different ways. This photo would be factory. Top photo shows a relay floating in mid air. This is not factory. Need to trace wires. Possible add on Headlight Relay.

If I'm not to late, we need to take the ECU out of the picture before you open up the harness. With battery cables removed, C103 disconnected, disconnect both ECU connectors. Check for continuity between D1_5 and D2_4 again. If continuity still exist, problem should be within the harness, otherwise suspect ECU (internal short).

Not sure if this is the wave or not, but I get a lot of single finger salutes, some come from Jeeps. Doesn't it means I'm number one?

Its a switch. Should close around 190°F.

Radiator Temperature Switch. Should go to the Cooling Fan Relay (Relay in bottom picture). Source vacuum for EGR (Bottem of EGR solenoid). Top is a screened vent for EGR.

It seems you got a Red wire touching a Yellow wire in the Engine Control Harness. Backtrack wires from D1_5 and D2_4 to their Splices. Also look a Fuel Pump Relay Block Pin_1 and Pin_5. Backtrack wires to the same Splices.

Forget I mentioned the firewall. Its gotta be the second photo.

Take the same measurement except this time disconnect C103. Back towards the firewall.

Disconnect both battery cables. Measure continuity between D2_4 and D1_5. Do you have continuity (0Ω's)? Stop cutting the wires.

Yes or No. Does D2_4 have voltage (B+ Hot at all times) with KEY OFF?

Check vacuum hose between manifold and MAP sensor for leaks or plugged line.

Did you ever have a winch or Class III Towing? Wire gauge looks heavy. Can't find anything in electrical manual.

If your talking about the Door Jamb Switch, it doesn't matter. Switch is dual (two contacts} switch to ground. Thanks eaglescout526. I've heard its a nightmare switch.

Good question. Do it with KEY OFF and with KEY ON. No need for engine running.

I see now, both wire are BLK/WHT. You need Pin B.

Remove Fuse (Gauges 7.5A) and try grounding the oil sensor wire again. Something is shorted.

Pin B (BLK/WHT) Don't know. This is new to me. Suspect Ignition Key Warning Switch.

LH Door Jamb Switch is a dual (two wire) switch to ground. One for lamps, one for buzzer. Technically speaking buzzer shouldn't work with the KEY OUT. I think removing wire from C276_B might shut off buzzer. Not sure what it will do for the Headlights ON buzz (doesn't seem to be tied into it). If you try this, let us know.

Check out Dark Forest Green. Run that by the wife.

Great find. Keep it as is.

I think so, traps prime (KEY ON) pressure, prevents fuel rail from draining back to the tank (long CRANK times).