1. Try using one of the individual door trigger wires. If you go to the purple plug at the BCM, the driver's door trigger is tan, and the blue/white gets the passenger doors.
Just tie your domelight supervision output directly into the tan driver's door wire, and see if the outside lamps come on that way.
Since the individual door trigger wires are low current, you won't need to use a relay either.
2. The 555T isn't so great...it's the one where you have to read the car's R-code with a meter, and then set a bunch of DIP switches on the 555T to match it, correct?
When you start the car with the key, the 555T allows the car's original R-code to pass right through, so of course it works perfectly every time. When you use the remote start, the 555T puts out whatever code you have set with the DIP switches. It might be close to what the car wants, but it might not be exact.
I don't think they've been selling 555Ts for at least a few years now...everyone's using the 555L. The L doesn't have DIP switches, and you don't use a meter; it's a self-learning piece. And the coolest thing is, EVERY time you start the car with your key, the L is reprogramming itself.........so if the car's resistance value changes just slightly for whatever reason, the L will keep right up with it.
So definitely ditch the 555T and use a 555L instead.
3. Here's a DEI tech sheet for your car. I've done lots of these trucks, and I can verify that all the colors and locations are perectly accurate. (Well, I haven't done window modules....I've verified everything except the window wires.)
| ITEM | WIRE COLOR |POL| WIRE LOCATION |
| 12V|red |+ |ignition harness |
| STARTER|yellow |+ |ignition harness |
| IGNITION|pink |+ |ignition harness |
| SECOND IGNITION|white |+ |ignition harness |
| ACCESSORY|orange |+ |ignition harness |
| POWER LOCK|lt. blue |+ |brown plug at BCM *1 |
| POWER UNLOCK|white |+ |brown plug at BCM *1 |
| LOCK MOTOR|gray | |drivers kick panel |
| UNLOCK MOTOR|tan | |drivers kick panel |
| DISARM DEFEAT|tan | |passengers kick panel |
| PARKING LIGHTS +|brown | |lt. blue plug at BCM *1 |
| PARKING LIGHTS -|white | |lt. blue plug at BCM *1 |
| HEADLIGHTS|white |+ |lt. blue plug at BCM *1 |
| DOOR TRIGGER|*2 |- |BCM *1 |
|FCTRY ALRM DISARM|lt.green |- |drivers kick *4 |
| TACHOMETER|white | |ECM *3 |
| SPEED SENSE|dk.GREEN / WHITE | |ECM *3 |
| BRAKE WIRE|white |+ |brake pedal switch |
| HORN TRIGGER|black |- |brown plug at BCM *1 |
| WIPERS| | | |
| LF WINDOW UP/DN|blue - brown |A |drivers door switch |
| RF WINDOW UP/DN|blue - brown |A |passenger door switch |
| LR WINDOW UP/DN|blue - brown |A |LR window switch |
| RR WINDOW UP/DN|blue - brown |A |RR window switch |
Notes:
Note: This vehicle has the passlock II immobilizer system that, when adding a remote start, must be interfaced with. Use DEI part 555t or 555L. Note: Diesel glow plug, dk. blue(-) located at the instrument cluster. *1 The BCM is located behind the drivers side of the dash. The plugs on the BCM face towards the rear of the vehicle. The parking lights are in pin A5 and the headlights are in pin A11. *2 Use tan for the drivers door located in pin B4 of the purple plug, the passenger doors are a blue/white in the lt. blue plug, and the rear hatch pin is a pink/black in the lt. blue plug. You must diode isolate these wires. *3 ECM is located near the battery, down low, between the fender and the fan under the black plastic cover. On the 4.3L, the tach wire is at pin 20 in the connector labeled "red", and VSS wire is at pin 3 in the connector labeled "black". On the 4.8L, 5.3L, and 6.0L, the tach wire is located at pin 10 in the "red" connector, and VSS wire is located in pin 50 of the "red" connector. *4 Also found in the purple plug of the BCM.