2005 Toyota Scion TC radio wiring issue

I’m not a mechanic by any means, so any help will be accepted and I’ll be grateful.. I bought my 2005 scion TC (used) with an after market radio installed and with no sound. The radio is fully functional… Behind the radio when i pulled it out i found one harness/bracket of wires connected and a bunch of loose wires.

I figured maybe this was ok and decided that the speakers were blown or no longer in the car, so I ordered speakers and amp and me and a friend installed them (mainly him). the amp has power and it is all ran/connected/wired correctly to my knowledge, But still no sound. So if anyone could help I would be very grateful. And I’ve checked all fuses connected directly to amp and radio (HU) itself but not the ones in the cars fuse box???

I’ve read and asked around and most answers are i need to fix the radio harness/bracket or find a way to connect the rest of the “Loose wires”. I can figure out details of radio(HU)/amp/speakers when and if needed.

Have no idea what your aftermarket radio wiring is but I can provide you with the stock wires.

Most radios need power on the two biggest wires and ground on the black wire, then hook up one speaker on two of the little wires, if you get no noise.. radio is no good typically.

One fuse in the engine compartment (RAD 1) 20 amp fuse BLU wire
One fuse in the instrument panel location (ACC) 7.5 amp fuse GRY Wire

radio diagram


5 thoughts on “2005 Toyota Scion TC radio wiring issue”

  1. I plan to buy a new HU, but the radio only had one wire harness connected to the back of it when i removed it from the console, i dont know much but im almost certain there should be 2 harnesses back there instead of one and a bunch of loose wires.??? And thank you for the reply. This has had me stumped for days and stuck without sound sucks after dumping money into amp and speakers.

  2. You should see a wire harness with the corresponding colors similar to the diagram provided above. If they are all in one harness or two makes no difference as long as you see all the wire colors shown in the diagram.

  3. The harness connected the HU only had 3 wires and the antenna connected. the wires were red/yellow/black. theres a blue in the harness but its cut in half and both ends taped off.

  4. Just installed new HU sony (cdx-gt66upw), HAVE SOUND NOW! But have new problems… Amp doesnt go off with car, and subs aren’t pushing sound, only car speakers???? and amp remote doesnt have power?

  5. There should be a wire marked “remote” coming off your New stereo, this will need to be connected to the Amp on the “remote” location. This turns the amp on to push power to subs. You will need to connect your constant power to amp with a Key On power only location if you want the power to shut off with the key off.

    For testing you can use a jumper wire on the amp to attach the Remote and constant B+ just until you run a wire from the stereo to the remote location on the amp.

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