What is in the 20-pin radio harness?

Discussion in 'Gen 2 Prius Audio and Electronics' started by egg_salad, Apr 28, 2018.

  1. egg_salad

    egg_salad Active Member

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    I've seen some threads about this, and some Google detective work is helping, but I have yet to find comprehensive information about what is in the 20-pin radio harness in total.

    What I do know so far:

    the two pins that need to be jumped with a 68-ohm resistor to maintain HVAC functions when doing an aftermarket radio installation.

    1 or 3 wires that come in from the steering wheel radio controls.

    So far, those are the things I know I will have to take care of when installing an aftermarket radio. Obviously there are a dozen plus more pins in that harness, and I'd like to know what else is going on in there that I might NEED to deal with and/or WANT to deal with for other possible functions or upgrades. Can someone help? A comprehensive pin out would be super helpful, but I can't find one.
     
  2. ChapmanF

    ChapmanF Senior Member

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    Permit me to suggest techinfo.toyota.com, where you can find 2 very interesting things:

    • The New Car Features manual, with its section on the car's communication networks, which will explain to you exactly what's going on with the 68-ohm resistor business, etc.
    • The Electrical Wiring Diagram, which will tell you all about exactly what's in that 20-pin connector, what color and which pin (not to mention part numbers for the connectors and pins, should you need any of those).

    -Chap
     
  3. Elektroingenieur

    Elektroingenieur Senior Member

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    @ChapmanF makes a good suggestion. Besides the two references he mentions, also see the Repair Manual, under Audio/Visual: Audio Visual System and Navigation: Navigation System. Each of these sections has Terminals of ECU pages, with descriptions of the signals present on each terminal, and Circuit pages that explain some of the circuits and signals in more detail.
     
  4. KK6PD

    KK6PD _ . _ . / _ _ . _

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    Download the car service manual pertaining to the electronics in the car. It is a wealth of good info about what is there, and if you read prints as well as I do, it becomes a roadmap to fun!!
     
  5. egg_salad

    egg_salad Active Member

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    I do have the repair manual, 2006. I guess I'm having difficulty deriving the information I want from the information presented. I can understand, for example, that the radio has 3 connectors, R 3(A), R 4(B), R 5(C), but I'm not finding out how to know which one of those connector numbers is the 20-pin. (And I'm pretty sure the radio actually has 4 connectors, but I haven't had it out, so I might be mistaken.)

    Also, the radio is showing 20 connection points, but obviously there are more, since the one connector I'm looking at has 20 pins all by itself.

    Apologies for my ignorance, and thanks for your help.
     
  6. Elektroingenieur

    Elektroingenieur Senior Member

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    From the notation you mentioned, you’re probably looking at the “Multi–Display and Audio System with Built–in Amplifier” pages in the System Circuit chapter of the Electrical Wiring Diagram, which Toyota publishes as a separate book from the Repair Manual.

    “R 3(A), R 4(B), R 5(C)” means there are terminals of three connectors shown in that depiction of the Radio and Player, and the terminals labeled there with symbol Ⓐ are on connector R3; with Ⓑ, on R4; and with Ⓒ, on R5. For example, the GND terminal on the Radio and Player is labeled 7 Ⓐ. This means it is terminal number 7 of the connector with symbol Ⓐ, that is, terminal 7 of connector R3, sometimes abbreviated as R3-7.

    The letter designations are arbitrary. For example, when we meet the Radio and Player again on the ”Multiplex Communication System – AVC–LAN Bus” pages, it’s labeled “R 5(B), R 6(A).” This doesn’t mean there is anything different about connectors R5 or R6, only that to explain the multiplex system’s wiring, there was no need to show any terminals from connector R3, so no letter symbol was allocated for it there.

    The System Circuit pages sometimes show terminals from the same connector on different pages, if the terminals are used in different systems. The same terminal can also be shown on more than one page, if it’s used in more than one system.

    The shape and terminal numbering of each connector are shown in the Connector List chapter of the Electrical Wiring Diagram. There we see that connector R3, for example, is a 10-position connector. The Electrical Wiring Routing chapter shows where to find each connector on the car; R3, R4, and R5 are all shown on the Position of Parts in Instrument Panel pages.

    The letters in the connector designations also tell you the general area of the car where the connector is found; “R” means the center of the instrument panel, for example, not a class designation for a resistor.

    Many connectors are also shown in the Repair Manual proper, in the Terminals of ECU pages for each system. These pages have tables explaining how terminals are used. For example, under Audio and Visual System, the table includes this entry for the GND terminal:

    Symbols (Terminal No.): GND (R3-7) - Body ground
    Wiring Color: BR - Body ground
    Terminal Description: Ground
    Condition: Always
    Specified Condition: Below 1 Ω​

    The Repair Manual also includes circuit troubleshooting information. For example, the Radio Receiver Power Source Circuit pages show connector R3 in the second step of an Inspection Procedure, in which the voltage between the supply and ground terminals is checked.

    Note the hint “*1: for 6 speaker system,” which means that the information shown with the note symbol “*1” applies only if the car has the six-speaker sound system. Notes like these appear often in the documentation for systems that vary depending on the car’s grade (trim level) or factory-installed options.
     
  7. egg_salad

    egg_salad Active Member

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    Okay, here's what I've learned so far. I will append this thread as I learn more information. Saved here for posterity.

    First of all, Toyota tends to use the same connectors across many years, model lines, and trims. There are pins, therefore, that will never be used on any G2 Prius. More on this later.

    Fact 1: ALL G2 Prius will have the following 5 pins implemented:

    Pins 6, 7, 8 - send a matrix of information from the steering wheel controls

    Pins 9,10 - send digital information from the radio to the MFD. These are the pins that must be jumped with a 68ohm resistor when installing an aftermarket radio to "fool" the MFD into believing the factory radio is still present. If this step is skipped, HVAC and NAV (if equipped) will no longer function in the MFD.

    Fact 2: If the factory radio includes an AUX function (and port):

    Pin 15 is right channel audio
    Pin 16 is audio common
    Pin 17 is left channel audio
    Pin 19 is AUX sense - that is, it tells the radio whether or not something is plugged into the AUX port. If not, the function is disabled in the radio.

    Here's where I start to get sketchy:

    If the factory radio has JBL/Bluetooth phone functions, I believe that there are 3 pins that go to the factory Bluetooth microphone. There MAY also be pins that send line-level audio to the amplifier. I say this because there are aftermarket radio install kits that have RCA plugs that *appear* to take line-level outputs from the aftermarket radio and send them to the JBL amplifier. There also appear to be wires in such kits that send power, ground, and amp turn-on signals to the JBL amp.

    If the car has factory NAV, there seem to be pins that take audio from the NAV system and feed it to the radio.

    After that, pins in the 20-pin connector that will NEVER be used in a G2 Prius. Many of them are implemented in cars, including the G3 Prius, where NAV and backup camera are fed to the screen on the factory radio (as opposed to the MFD screen). Things like the camera feed from the backup camera, a feed from the Vehicle Speed Sensor that prevents operation of NAV when the vehicle is in motion, a feed for Reverse Sense, that turns on the backup camera when the vehicle is placed in reverse, etc.

    I will append/edit this information as I learn more.
     
  8. George!

    George! New Member

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    I wanted to pitch in the fact that without the factory radio installed and without that resistor, it's not just the HVAC that doesn't display. The MFD doesn't display outdoor temp, status of hybrid drive, or average MPG. The screens are there, they just are blank. I know this because I yanked my factory deck today, and am trying to find a 68 ohm resistor. Man, do I miss Radio Shack. :)
     
  9. George!

    George! New Member

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    Interestingly enough, after I hooked up the resistor to the harness, it showed the MPG accrued on that tank. In other words, all the calculations are still performed, you just won't see it until you get that resistor installed.
     
  10. JB1126

    JB1126 New Member

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    I know this is an old post. Hoping to gain some answers. I'm upgrading to an aftermarket radio in my 2009 Prius. I have the 86120-47200 radio, has an empty aux input but other 3 harnesses are used. I know what 2 of the harnesses do and how to connect them, but the 20 pin remains puzzling. I'm good with pins 6-10 and how to hook them up. But my harness has alot more wires and I don't know what to do with them. I still have these pins...

    1 - Black
    2 - White
    3 - Purple
    15 - Green
    16 - Gray
    17 - Red
    19 - White

    Could they just be extra and unused in this harness?

    2 photos attached. Thanks for any help!
    2019-11-18 10.02.01.jpg 2019-11-18 10.01.41.jpg
     
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