2000 Accord EX steering wheel radio controls wiring
 

Hello everyone, new guy here.
I'm in the process of tackling a project with the radio controls on the steering wheel. I read a lot of topics about people adding them to their stock radio and it seemed impossible to most, but I'm going the other way around. I have a fully loaded EX with the radio controls and replaced my radio with an aftermarket one, by the way might I add it's a HUGE improvement in sound quality even on the stock speakers, the stock radio sounded like junk, it was the double din single cd type, I don't blare my music or play any annoy rap so the stock speakers are plenty good for me.

Anyways here's what I know and what I need to know. First of all I'm very skilled at soldering and rewiring car's electronics, I have no fear of hacking or cutting into wiring harnesses or adding wires, it seems like the other posts I read people stopped when they heard anything about that. I found the 2 pins on the aftermarket radio that controls volume up and down by grounding them, I can also add relays if the input from the wheel controls goes high to 5v or 12v. What I've seen on many other cars (I have a vast amount of my experience with Chrysler products in particular) is that the cruise/radio controls on the wheel are multiplexed to cut down wires running through the clockspring. I'm not sure if this is true on the Accord for the 3 radio buttons but I'd assume so. If that's the case I'd need to build a de-multiplexer that will take different voltages or resistances and activate one of 3 relays or transistors.

If anyone has any feedback or input on this topic, please let me know. Right now I'm trying to gather as much information as possible and make a plan of getting this tackled. I don't have any wiring diagrams or service manuals for it and I haven't dug into any of the car at all except splicing into the radio harness to add the new stereo, that's all I did and looked at so far as I just purchased the vehicle for $9,000 with 51k miles on it, not bad at all.
Thanks for reading.

This is the EX-V6, correct?

Yes, EX-V6 3.0. Has leather and a sunroof if that helps narrow down the trim level even more.

Okay, only the EX-V6 has the steering wheel remote switch, not the EX-4 cylinder.

The radio remote switch runs from the radio via a Grn/Red wire (Green wire with Red stripe) through cavity terminal #2 at C401 a (22-P blue connector located above the driver's under-dash fuse/relay box), then connected to the cable reel via a 4-P Blk connector, which then runs through a Blk or Grn wire to the radio remote switch. Does not run through the multiplex control unit.

Ah, very helpful. Now I know what to trace down. I didn't even know there was a multiplex control unit in there or what it even does, could also be Honda's fancy name for a BCM maybe.
So pin 2 on the blue radio connector, green wire with a red tracer, through a connector and to the clockspring/cable reel. I have to get updated on all these terms Honda's uses for things, they have unexpected names for a lot of things.

The use of a single control wire to control 3 different buttons tells me it's a multiplexed control meaning there's different resistance values being feed through the same wire for each of the different buttons. That alone is a huge piece of the puzzle.

Yes, Honda's multiplex control unit is their fancy name for a BCM (body control module). On your model year Accord, there is the driver's multiplex control unit, the passenger multiplex control unit, and a driver's door multiplex control unit.

You're also correct that there are probably different resistance values for each of the different buttons, as it is only using a single control wire. See attached pic. Not disagreeing with your meaning of the term "multiplexed control" however, Honda doesn't include that as part of their multiplex control system.

I see, thanks for your input, it's extremely helpful. This is my first Honda so I'm just starting to get into the forgien cars with it, before all I ever worked on was domestic vehicles. I'll do some tests on the wire in pin 2 of the radio connector and see what I come up with.

I'm going to move your thread to the Audio/Video Electronics section on this forum. That section has a A/V electronics guru, "keep_hope_alive", who can probably provide you any other exact info. with your project.

Sounds great. Thanks a bunch for all your help.

No problem. I am pretty sure keep_hope_alive has done the project you're describing before.