What causes a truck radio to constantly reset itself, like every time I turn off the truck?

The black wire on the aftermarket radio's harness can be screwed down to metal in the truck. This will be a good ground and will most likely be better than the ground in the harness coming from the truck.

The first set of colors above is what will be on the aftermarket harness you are wiring into the truck. These are:

Yellow: constant 12V (memory)

Red: switched 12V (accessory)

Black: ground

White & White/black: left front speaker

Gray & Gray/black: right front speaker

Green & Green/black: left rear speaker

Violet & violet/black: right rear speaker

You may also have a blue, blue/white, orange, orange/white, etc. You won't need to connect these to anything in your truck.

The second set of colors: Tan, gray, lt green, dk green, etc. are the colors of the wires in your truck’s harness that will be wired to the ones listed above.

If all else fails, you can take the truck to a car audio shop to have the hardwire done. This will cost about $25-$30 (not having the whole thing installed), just the harness.

Can having a bad ground not supply power to the aftermarket radio? --- absolutely, however, most stereos will use the antenna as a ground if needed but this isn't the best idea. You want to make sure you have the best ground possible.

Since the aftermarket harness and radio colors match up do I still follow the recommended color scheme that you provided earlier? --- yes. Aftermarket colors are 99% the same, but GM along with pretty much every other manufacturer use their own color schemes & they are all different. Just because there is a red wire in the dash doesn't mean it is a power wire & in most cases it's not. An example is a late model Toyota. It has a red wire which is a rear speaker lead.

Lastly, can I ground the black ground wire to any metal in the truck or does it have to be metal on the truck frame? In the 91 Silverados, there is a metal brace in which the tape player was sitting on can I ground the wire to that metal frame? -- Just as long as the metal bracket you are grounding to is mounted to more metal in the dash, you should be fine. Look towards the bottom of that bracket, there will be 2 7mm screws holding it in, if those screws secure to more metal it will be ok. I would give you a simple yes or no here, but I always remove that bracket before installing the new deck; because it always seems to get in my way. If you don't want to ground to this, take a ground wire to the under dash below the steering column, there's plenty of metal under there to ground to.

As a final thought, test your power wires with a digital multimeter and make sure that you have both 12V constant and 12V switched at the yellow & red wire (aftermarket harness) respectively.

I hope this clears things up, let me know if you need anything further.

OK. I didn't know you still had the harness intact. This makes it real easy then. Go to a car audio shop & ask for a Metra 70-1858 (Circuit City has the Metra 80-1858 which is the same thing but it's a smart harness that can connect to another harness made by Metra for Sony, Pioneer, Panasonic, JVC)

Once you have this "car side" harness, wire it to the harness that plugs into your stereo (the wire colors will match), then just plug in the harness to the plug in the car.

You haven't mentioned what parts you have or have not bought to install the deck, so just so your aware, you'll need"

Metra 70-1858 (wire harness adapter)

Metra 99-3000xx (dash kit with din opening available in several colors, ie. black, dk blue, burgundy, tan, gray)

Metra 40GM10 (antenna adapter)

Let me know what brand of stereo you have & what parts (listed above) you have purchased. If you already have these & plug the harness in but don't get power then we'll have to go through some troubleshooting steps.

Ok, have you tested both the yellow & red wires on your harness for 12V (yellow will have 12V all the time, red will have 12V when the ignition is on)

If the yellow wire does not have power, then you'll need to look for a different fuse. It is easier just to test them all, but if you just want to try to locate the one for the memory wire then look for one labelled as the dome light or cigarette lighter or something else that you know has power when the car is off. Remember it's not necessarily labelled as the "radio" fuse. If you do find another blown fuse (under the dash or under the hood) then replace it. If it blows again right away then you know there is a short in that circuit. Look back to where the factory harness is routed up from when it was connected to the tuner pack under the dash, make sure it's not rubbing on any metal surfaces. If it is clear, but you still cant get constant power through that circuit, you can always drop a power lead down to the ignition harness & hook it up to the large red wire there (remember to fuse it)

All of this can be done for the radio's red wire too. We just need to see what has power & what doesn't.

So test these wires & let me know what you find.