I have 2002 f150 truck the factory wiring harness has 2 illumination wires feed and ground. Not for sure witch to use.

AVIC-Z2

Check both with volt meter and use the one that gives prositive voltage when the parking lights are turned on. It may not be a full +12v if you have the dashlights dimmed. Start with the light blue/red wire.

thanks, will this let me dim the lights on the display

Not really. There are 2 brightness settings.

1. when the headlights are off

2. when the headlights are on.

When you turn the headlights on it will send a signal on the illumination wire to the Avic, it will see this and switch to the brightness setting 2. When you turn the lights off, the Avic sees this and goes to brightness setting 1. You can adjust the brightness in the Avic for each one (lights on or off) but it won't "track" from the dimmer of your vehicle.

Did that make sense?