Diagram for Nissan 2003 Frontier

Here is the 2002 information, use what you can but I can't verify the wire colors for certain:

|       ITEM      |     WIRE COLOR     |POL|       WIRE LOCATION        |
|              12V|green               |+  |ignition harness            |
|          STARTER|BLACK / YELLOW        |+  |ignition harness            |
|   SECOND STARTER|GREEN/  YELLOW        |+  |ignition harness            |
|         IGNITION|BLACK/ white         |+  |ignition harness            |
|        ACCESSORY|RED / yellow          |+  |ignition harness            |
| SECOND ACCESSORY|WHITE/ blue *1       |+  |ignition harness            |
|       POWER LOCK|yellow *7           |-  |*3                          |
|     POWER UNLOCK|yellow/red *7       |-  |*3                          |
|       LOCK MOTOR|blue                |   |*3                          |
|     UNLOCK MOTOR|GREEN / WHITE         |   |*3                          |
|    DISARM DEFEAT|purple or blu/red *9|   |*3                          |
| PARKING LIGHTS +|blue/red            |   |steering column             |
|       HEADLIGHTS|red, RED / blk *5     |+  |steering column             |
|     DOOR TRIGGER|RED / black *4        |-  |*3                          |
|         HOOD PIN|BLACK/ pink          |-  |*3                          |
|  FCTRY ALARM ARM|arms with lock      |   |                            |
|FCTRY ALRM DISARM|disarms with unlock |   |                            |
| DISARM NO UNLOCK|*8                  |   |                            |
|       TACHOMETER|pink/blue or black  |   |instrument cluster or ECM *2|
|      SPEED SENSE|dk. GREEN/ black     |2  |ECM *2                      |
|       BRAKE WIRE|BROWN / red           |+  |brake pedal switch          |
|     HORN TRIGGER|lt grn/red or brown |-  |steering column             |
|           WIPERS|*6                  |-  |steering column             |
|  LF WINDOW UP/DN|blue - blu/blk      |A  |at drivers door switch      |
|  RF WINDOW UP/DN|blu/yel - blu/wht   |A  |at drivers door switch      |

Notes:*1 Not required for remote start. *2 The ECM is located below the heater box to the right of the accelerator pedal, behind trim panel. The tach is in the top row, 3rd pin left of center of the plug. The VSS is in the 2nd row from the top, 4th pin right of center. *3 Located at the Smart Entrance Control Unit above the hood release in the drivers kick panel. The door lock wires only meter when turn the key in either door key cylinder. *4 If equipped with factory dome light delay, use GREEN/ red(-) for the drivers door and GREEN/ black(-) for the passenger door. Diode isolate each wire. The RED / black may also be found in the drivers A pillar. *5 These wires are for the low beams. For the high beams use RED / green(+) and RED / white(+) at the same location. *6 Use WHITE/ blue for intermittent, WHITE/ red for low, and blue/white high. *7 Unlock requires a double pulse. On vehicles without the factory alarm, can also find lt. GREEN/ red for lock and brown for unlock. *8 A single pulse to the unlock wire will disarm the factory alarm without unlocking the doors. *9 It is purple on the 2 door models, and blue/red on the 4 door.

http://www.velocitymotorsport.com/Second_Starter_Relay.pdf

I don't have the wiring information for just the DISARM wire on this vehicle. As far as my notes are concerned, it disarms with the unlock. You may have to set the system to pulse once to disarm the OEM alarm and pulse a second time for the unlocking of the doors. Is this a double pulse unlock door system on the vehicle ?