CivicInUse22

need the wiring diagram for the stereo in a 94 civic. Not the diagram stating where the wires on the stereo connect to the harness connector for aftermarket applications, the actual full wiring harness for the radio through the whole system. My radio isn't getting power and I volted the power with from the connector and Im gettin 0v and I need to trace back where the problem is.

TomCat39

Okay Stereo power is the Yellow/Red Wire as you may know. It runs from the stereo connector (C517) to the under dash fuse box connector (C501) and is controlled by fuse #23. On the other side of the fuse box it is the White/Black wire in connector (C922) that runs to the ignition switch. Beyond this is pretty pointless being you aren't reporting your car not starting. Power to the ignition switch is the White wire to connector C427 that then becomes the White/Black wire that goes to Under Hood dash Fuse #39 and #41 on connector C203. If it was there that the break was, your car wouldn't start.

If you have continuity through the full Yellow/Red wire. And if you get continuity on the white wire of C427 to the White/Black wire of C922 with the Key in the On (II) postion (battery disconnected), then it's not in the ignition switch. If you don't get continuity between those two wires when in the On (II) position then it's a problem in the ignition switch. Ignition switch Powers 4 wires total so could possibly power 3 critical wires while not powering the White/Black wire of C922 that goes to Fuse #23 and the stereo.

There is also the White/Blue wire that is constant power (tuner memory) that runs from Under Hood fuse #32 at connector C205 to the under dash fuse box connector C441. Comes out the under dash fuse box at C501 and runs to the stereo connector C517 still as a White/Blue wire.

Hope this info helps you.

TomCat39

Of Note, the FSM doesn't provide clear information on wires in or through connectors so is much more difficult to trace.

To get complete accurate tracing info through all connectors and such you need to purchase an ETM (Electrical Troubleshooting Manual).

They can be had for a fair price at helminc.com

Helms makes the preferred manuals and also sells the FSM (Factory Service Manual) to for a fair price.

The information I provided you in my previous post was pulled from the ETM.

Former User

The radio needs voltage from 2 separate power wires. Voltage test both fuses that protect the 2 power wires (ignition and constant). Click the fuses link in my signature.

TomCat39

Constant doesn't have a fuse in the under dash fuse box like the Yellow/Red ignition controlled power line does.

They both do correlate to fuses in the under hood fuse box though.

Constant is a pass through connection in the under dash fuse box.

Former User

Not sure what point you're making.

TomCat39

You said check both fuses for the power and constant. Didn't want OP confused trying to locate a fuse for constant power when there isn't one.

And if we were including the under hood fuse box then it's more than just two fuses in play.

Either way, could be confusing so providing more information for clarity.

Former User

Incorrect. Please carefully study the radio circuit. The radio receives and requires both ignition switch voltage from the dash fuse box and constant voltage from the hood fuse box.

nub

Constant power IS fused and comes from the under hood back up fuse shared with the ecu and clock.

TomCat39

Never mind, I did study the circuit in it's entirety. As can be seen in my first post.

You are removing extraneous information that doesn't apply when the radio doesn't work but the car runs. So removing Fuse #39, #41 only leaving #23 and #32 while I was including the full circuit back to the battery on the hot side. So in correction, if anything I was adding possible confusing information in the name of completeness.

Also I meant, but didn't convey correctly, constant isn't fused in the under dash fuse box while ignition power is essentially double fused one of them being in the under the dash fuse box.

However, I realized, none of us included the ground. Could have power and if the ground is bad, it wouldn't work and power up and potentially cause damage to the head unit (stereo).

OP you may also want to check your ground which runs from connector C517 (pin 14) to ground location G501 and is a Black wire. It is located under the dash to the right of the steering column about 2 or 3 inches up from where the ignition harness is clipped to the steering column (assuming all stock virgin wiring).

Once again this is all assuming you are running the stock stereo harness/plug

Former User

First post clearly states the problem is a lack of voltage. It just doesn't state whether the lack of voltage is at the radio's ignition switch or constant power wire.