Wiing for factory radio

You have to cut the factory speaker wires on both sides of the amp and solder them together.(bypass the amp) Pull out the factory radio so you can identify the color of the speaker wires or look at the wire colors on the back of the factory speakers.

see connection colors below and let me know if you have questions.

2004 Nissan Sentra wire colors aftermarket radio wire colors

Car Radio Constant 12v+ Wire: Pink, yellow
Car Radio Switched 12v+ Wire: Blue, red
Car Radio Ground Wire: Gray, black
Car Radio Illumination Wire: Red/Green, N/A (tape off factory wire)
Car Stereo Dimmer Wire: Red/Yellow, N/A (tape off factory wire)
there is no factory amplifier wire, blue (tape off radio wire)
Left Front Speaker Positive Wire (+): Pink, white
Left Front Speaker Negative Wire (-): Blue, white/black
Right Front Speaker Positive Wire (+): White, gray
Right Front Speaker Negative Wire (-): Black, gray/black
Left Rear Speaker Positive Wire (+): Light Green, green
Left Rear Speaker Negative Wire (-): Violet, green/black
Right Rear Speaker Positive Wire (+): Blue, violet
Right Rear Speaker Negative Wire (-): Pink, violet/black

Most factory radios do not have RCA outs, but most will have a remote wire. Usually used for a power antenna option. Your remote wire from the amp could be hooked to the power antenna wire on the factory radio and it would work great for turning on the amp. As for the RCA inputs on your amp, you will not be able to use them without RCA outs on your factory deck. Although most amps offer a high level input alternative and will use the standard speaker level out on your factory deck. This means the rear channel speaker wires from your factory deck will be used to feed the signal to the amp. You will have to check the instructions and manufactorer recomendations for the amp you are trying to hook up. Have fun and good luck!

Radio 12v blue/yellow + radio harness
Radio Ground brown - radio harness
Radio Ignition gray + radio harness
Radio Illumination green + radio harness
Factory Amp Turn-on N/A
Power Antenna N/A
LF Speaker +/- pink - purple +,- radio harness or amplifier
RF Speaker +/- lt. green - blue +,- radio harness or amplifier
LR Speaker +/- black - yellow +,- radio harness or amplifier
RR Speaker +/- red - white +,- radio harness or amplifier

Notes: If equipped, the amplifier is on the passenger side rear cabin wall.

Do you have the remote turn-on lead hooked up?

There should be 3 wires on the power side of the amplifier.

Ground - to the car chassis
Power - to the car battery
Remote - to the remote turn on lead from the head unit. (this emits a 12V signal to a relay inside the amplifier for it to turn on when the radio does)

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If the vehicle has a premium sound package - you need to use the remote wire to turn on the factiry amplifier.
If you want to use the power from the radio for the speakers, you must buy and install a factory amplifier bypass harness.

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Here ya go. enjoy!
2002 GMC Sierra C1500 Car Radio Wire Color Codes
Car Radio Battery Constant 12v+ Wire: Orange
Car Radio Accessory Switched 12v+ Wire: Yellow
Car Radio Ground Wire: Black/White
Car Radio Illumination Wire: Brown
Car Stereo Dimmer Wire: Gray
Car Stereo Antenna Trigger Wire: N/A
Car Stereo Amp Trigger Wire: N/A
Car Stereo Amplifier Location: Under the center console.
Car Audio Front Speakers Size: N/A
Car Audio Front Speakers Location: N/A
Left Front Speaker Positive Wire (+): Tan
Left Front Speaker Negative Wire (-): Gray
Right Front Speaker Positive Wire (+): Light Green
Right Front Speaker Negative Wire (-): Dark Green
Car Audio Rear Speakers Size: N/A
Car Audio Rear Speakers Location: N/A
Left Rear Speaker Positive Wire (+): Brown
Left Rear Speaker Negative Wire (-): Yellow
Right Rear Speaker Positive Wire (+): Dark Blue
Right Rear Speaker Negative Wire (-): Light Blue

What car are you looking for the wiring diagram for?

A simple line level converter would convert an input signal to a factory speaker - into a useable Low Level RCA signal for your amplifier.
There is your signal - now all you'll need from behind the radio is the 12V Remote signal.
Send me your make/model/year, and i will tell you which wire to use.

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buy a harness 4 your van.pull factory unit out read harness to see what color remote wire is. it should be blue.stripe some of the wire enough to tie remote wire.

If you have an electric aerial, you can tap into the wire to it. Usually a thinnish blue or orange wire. The electric aerial should have 2 or 3 wires going into it (depends on if the body connection is used for ground or seperate wire is used). The sense/control wire will typically be the smallest wire. It should change polarity when the radio is switched from off to on.