I have a 2003 toyota rav4 and I'm trying to install a new Pioneer double din stereo. I've wired almost everything up correctly and it runs without any issue, except the stereo always thinks that I'm driving, i.e., it thinks that the parking brake is always disengaged. This means that I can't use certain functionality in the stereo.

Below you can see:

  • the parking brake switch (brown box)
  • red and black wire which was originally there
  • light green wire which is the parking brake wire that comes with the Pioneer harness.

Parking brake switch

The instructions in the Pioneer manual say that the light green wire should be connected to the power side of the parking brake switch, however, the switch in the picture only has one wire coming out of it (the red and black one). Thus, I assumed that the red and black wire must be the power in side. As you can see, I connected the light green and red/black wires using a wire tap connector.

The problem is that the Pioneer stereo still thinks that I'm driving, even when the parking brake is up.

My questions

How does the parking brake switch even work? What happens when the parking brake is pressed down? Does that close a circuit, thus grounding the red/black wire? Shouldn't the switch have a ground wire coming out of it somewhere (it only has the red/black wire)? Or since the switch is connected to the metal chassis does it not need the additional ground wire?

I read something about Pioneer stereos requiring a high-low-high signal in the green wire at a particular frequency, this is pretty confusing to me and it's very hard to find documentation on the subject.

Thanks for the help.

  • 1
    Welcome to Motor Vehicle Maintenance & Repair! If you just ground the light green wire, it will solve your issues. The stereo will believe the parking brake is always engaged and all functionality will work at any time whether parked or in operation. While this is supposed to be a safety feature, to me it's one of the stupidest things I've seen. Why? Because it's easy to bypass during installation. If they really wanted it to be a feature, they would have engineered it better. Realistically, I think they are just covering their butts. Ground the light green wire and call it a day. – Pᴀᴜʟsᴛᴇʀ2 May 1 '18 at 10:17
  • You have put the green wire on the wrong side of the brake light switch. – Moab May 1 '18 at 15:13
  • @paulster2 Thanks for your input. Turns out I just didn't install the wire tap correctly... haha. This model of pioneer requires you to un-ground, ground, then un-ground the green wire sometimes to "prove" that you're really parked. So having it hooked up to the parking brake switch was the right way to go in this case – Filip Kilibarda May 7 '18 at 5:42

Turns out I didn't install the wire tap properly, thus current couldn't flow between the green and red/black wire. Once I fixed the wire tap, it worked as expected.

I also figured out the answer to several of my other questions,

What does the green wire do?

Holds a 3V signal when the stereo is on. When the green wire is grounded, some stereo functionality will be opened up. You can test this by touching the green wire to the chassis and watch some stereo buttons fade in and out.

What does the red/black wire do?

It carries a 12V signal when the car's key position is at on not when it's at acc.

How does the parking brake switch work?

First, notice that there is only one wire coming out of the switch. Where's the ground wire? Well, the switch is grounded directly to the chassis of the car so there is no need for a ground wire.

When the hand brake is down, it pushes on a little black pin that completes the circuit, grounding the red/black wire.

In other words, when the hand brake is down, the red/black wire is at 0V, when it's up, the red/black wire is at 12V.

What is the high-low-high signal required by the Pioneer?

Note: It's my understanding that only newer Pioneer models require the high-low-high signal, so if you have an old model maybe this doesn't apply to you

It's been suggested that simply grounding the green wire is all you need to do to get the stereo to function properly. Although this will work in some cases (in the limited testing I did), it will fail to provide the high-low-high signal when needed, thus disabling some stereo functionality .

In some cases when starting up the stereo, the Pioneer will give a prompt saying that you must pull the hand brake up, down, then up again, in order to use a particular feature. This is the high-low-high signal the Pioneer needs.

  • Hand brake up -> circuit open -> green wire not grounded -> high signal
  • Hand brake down -> circuit closed -> green wire grounded -> low signal
  • Hand brake up -> circuit open -> green wire not grounded -> high signal

I have an AVH3100-DAB and all I needed to do to be able to watch videos was to tie the light green wire to the grounding (black) wire. Turns out there was a red connector attached to the end of the green wire, much like a bridge. Basically deisolate the black wire for a few millimetres and insert that portion into the red bridge, and voila! Of course, you can attach the green wire to the handbrake signal wire too, if you want to be unable to see videos while moving, which is safer.


If you have a newer poineer, you may not even need this wire. There's a secret hidden button on the home screen that unlocks video functionality while driving. As for the double-tap with the parking brake, you can buy a small chip from Mesa that does that for you. I have mine wired with it. Be aware it will still keep that annoying driving warning at the beginning.

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