Use OEM Mic with Aftermarket Headunit

Hats off to IIonPilgrimg for his persistence in helping me see the forest for the trees. With his assistance I was able to retain use of the factory MIC in my 2007 Double Cab. In the end, I used the wires on the truck’s K9 male 16-pin connector to accommodate ALL the wiring connections and left the Maestro (iDatalink) harnesses intact. The K9 connector is the primary connection to the factory JBL head unit and is not used in Gen2 Tundras (and other Toyotas) for the Maestro / Aftermarket HU installation.

While it is possible to make up the right connections on the back of the K9 connector without cutting some of its wires, I elected to cut those I needed as it made soldering the leads much easier. Once the necessary wires were cut, I folded the plug and remaining wires back on the main bundle and secured it with Tesa tape to have it out of the way for soldering the CMS connections.

To address the impedance / echo issue, I contacted IIonPilgrimg to see what size of resistor he used for his 2008 Double Cab – basically the same truck as mine, his is just one model year newer (See photo). Then I used Jeff Bezos’ company to purchase and deliver the handful of parts needed for the task. Once all the soldering was done, I used metal tape to affix the 12V --> 5V stepdown converter to the tubular steel cross-member to function as a heat sink.

After buttoning up and finishing the install, I arranged a call to IIonPilgrimg from my ’07 and he took the call in his ’08. Crystal clear and echo free on both ends – a complete CMS success! Thank you, IIonPilgrimg!!

 

amazing! Kudos to you and @IIonPilgrimg on a job well done. If you could mass market these I am sure the appetite for this would be robust. If someone could figure out a plug and play option for this, even better. And for the 2.5 generation, it would be incredible!!!! A lot of us (me included) are not confident enough in our skills to tackle the cutting of oem harnesses and soldering, etc.

 

Mr_Keith,

Thanks for the kudos and affirmation.
Your persistence is rewarded two-fold: The tech works and I'm no longer the only one with a functional CMS.

shawn474,

On Page #3, Mr_Keith pictured the (2.5 Gen) 28-PIN Maestro "Plug C." (attached)

I've not ceased contemplating where we left off and whiteboarding with Mr_Keith has me thinking about:

(Gen 2.5 only -- Gen 3.0 needs R&D)
An exchange program for those requiring plug n play.
Should work for Single-Cab or Double-Cab.
If equipped, MIC #2 (rear?) must be disabled, which means dropping the overhead console and unplugging it... (need to see one first-hand)
A) Separately obtain a Maestro harness and mail in Plug C. *
B) Specify which MIC Plug (2.5mm vs. 3.5mm) when ordering.
C) In exchange, you receive Plug C modified with a CMS unit pre-wired.
D) Plug n Play.

(Gen 2.0)
At present, no Male K9 plug is readily available in the US market.
So the best option is cutting Female Plug K9 (will not be useful for other purposes regardless).
[Self-Note: ID PINS #3,#4,#6: #5 is Batt+, Radio fused]
Connections can be crimped (easier) or soldered (better).

* Other brands might be possible (R&D needed)

 

I believe I have a maestro wiring harness lying around that I could send you. I would be happy to pay and beta test a plug and play option. The only issue is dropping the headliner to disconnect the rear mic......i hear that is a pain in the ass . But I would be willing for the greater good!!!!!

 

OK

I've identified the male pins used in the Maestro #28-Pin connector. #6 must return to GRD (#4 - 5V to MIC) to make CMS work for a plug-n-play Gen 2.5 installation.
In the Toyota harness this goes to ground through the head and the Maestro HRN (TO-1 or TO-2) harness is blank on this pin.
Otherwise, this problem wouldn't exist for Gen 2.5, although the dual-MIC (might) be a problem for those equipped. Don't know until tested.
Might hope Toyota retained the same pins when changing the plug (again? -- for Gen 3.0), so the pins are similar for all Gen's.
I've found the male counterpart - photo attached. It's possible the tab sticking up must be trimmed.

2008 (#K9) and 2018-2019 (#J135) MIC diagrams are attached. SGND/SNS2 wire is the problem (#J135 only).
For Gen 2.0 this GRD happens in the factory harness, rather than through the head. It's not on the diagram and perhaps goes through shield.
The pins cost $0.05 ea, which doesn't sound like much. However, a minimum order is #12,000. (Perhaps they'd be useful in other positions also)

Unlikely shawn474 will want to cover this R&D by himself. While that's the final piece of the puzzle, I'm not sure there's sufficient demand to warrant the expense...
...Considering a Maestro (or other brand) harness is also needed for modification, and the size of MIC plug (2.5mm vs 3.5mm) depends on the HU being installed, it's a custom job / special order scenario.
It's possible only JBL/Separate amp equipped trucks have a mic?

Route and stare at the free black puck vs. send in your harness with a specs list and $100, then wait a week+ to install your new radio. Likely, demand would be less than hoped.

 

A bit more research / information. Although ad-heavy with pop-ups, I've found this site useful: https://pinoutguide.com/

With so many configurations, the solution would be a CMS add-on unit with pins crimped to wires but NOT inserted in a plug. Instructions where to insert them must be vehicle specific. Problematic if inserted incorrectly. Best to include a handy pin removal tool: a nice bonus. A pre-pinned CMS would also work for 2007--2013 Tundras with plug #K9. There is no male #K9 plug available so, direct connection to correct female pins would be required. (Heat-shrink / tape wrap to prevent crossing wires)

Maestro HRNHRRTO1 has a "C" accessory plug (28-pin) while HRNHRRTO2 integrates it into the main harness.
Neither has a male for #K9 (2007--2013). (They recommend TO1)
For 2014-2020 Tundra, they recommend TO2. (2021 may be a cross-over year)
HRNHRRTO3 is specific for 2020-2021 Tundra, 2020-2022 Sequoia, 2020-2023 Tacoma, 2020-2024 4Runner, and some others.

Then...
2022+ Tundra uses new radio plugs and (true to form) the location of MIC wires depends upon whether you have a built-in or separate amp system. For both, there is only one MIC:
There is a #30-pin plug (#I18) and a #28-pin plug (#I19).
Built-in amp system: MIC wires are on #I18 at pins #21-25.
Separate amp system: MIC wires are on #I19 at pins #17-21.
They have not (yet) developed an HRNHRRTO# harness for this new plug configuration.

(attachments)

 

There are not two mics in any of the trucks.
That 18-19 EWD denotes (*10) for the wires going to one of the mics and (*9) for the others. The page before it has this

They moved the location of the mic from the center overhead console to a separate little spot directly over the drivers head (by the sun visor) but never changed the part number for the overhead console so it still has the empty mic “grille” in it.

 

VERY interesting stuff and a lot to process……thanks to Tim and rainman for thinking this through and being much more knowledgeable than me! It will probably be a while before I can drop my headliner to do any R&D but am definitely interested in trying to do whatever I can to help figure out the known aftermarket echo issue. I am not in a position to absorb the cost totally of ordering that volume of supplies - I have no doubt that if this gets figured out and are reasonably confident that this will “cure” the aftermarket echo that many will purchase. I am willing to contribute to that purchase if anyone else is interested

 

There's so much code to miss on the schematics. That's amazing! Thanks RainMan_PNW.

Shawn's Tundra is a 2019 CrewCab: Perhaps he can show a pic of the grill location above the driver's head?

I will likely get a sample pin in my hands to confirm it's appropriate then order a min quantity. If an average of 6 pins are needed for each unit, 2,000 can be assembled to satisfy immediate demand (presuming it would be more than #2 or #3). As a template for 2007--2013, I'll reconstruct mine using pins rather than solder.

 

Which pins are you looking for specifically?

 

Looks like they saw me shopping, as 1 or 10 can be ordered now. (Plus their $8.00 shipping fee)
I believe it will be TE Connectivity #1802190-1 (although the tab sticking up vertically may be obtrusive)

All other measurements appear correct to fit in the Maestro harness male connector, or plug directly into the Toyota female pins.

 

Have you found details on the mating plastic connector housing for the Maestro? That little fin is part of the connector/terminal locking and off they aren’t the same “series” then they won’t work in the housing even if the pin size is a match.

 

Keep meaning to reply: No.
Hopefully, this pin can be one size fits all because the Male plug housing is custom, or obtained in bulk through Ali-mart.
There is no such thing as an original Male plug -- it's part of the factory radio into which the female harness snaps.
So, we'd prefer to tap into the Male plug others have designed as a mate. Regrettably, it could vary by harness Mfg.

 

Reference the attached circuit. (This is for a 5th gen 4Runner, but thought it'd be appropriate since the discussion is centered around interfacing Toyota's OEM mic with aftermarket head units - so discussion is tech/design based and not vehicle specific). I've installed this circuit in three different 5th gen 4Runners. One SR5 and two Limiteds. They both have 28 pin connectors whose pins are easily identified; however, the SR5s require a +5V power input to MACC and the Limiteds do not (they uniquely possess Toyota Connect with a telematics system that powers the microphone via the Data Communications Module (DCM)). I set the potentiometer at mid-range (25k) as a starting point. The circuit was constructed with a simple small breadboard, jumpers, 1:1 audio transformer, with trimming pot and simple caps. I tapped the appropriate wires right behind the 28 pin connector with T-tap connectors. People who call the owners of the vehicles state that there's a swooshing sound, or the sound is in and out, or can't be heard at all. Just not good results.
Has anyone else gotten different results from a lesser design? Or doing something different? Sort of desperate to get this issue resolved.
Would appreciate any feedback!! Thank you!

 

Only two verified, to date -- Both in Gen 2.0 Tundra. Your knowledge base is likely over my head. I would not be able to create that diagram.

For Q&A:

A) Why a 1:1 Transformer? *
B) Why a 50uF cap in the MCO+ line, and why is the resistor touching MCO-?
B)1) My gut: Caps or the Transformer are the cause of 'swooshing' (switching on/off or fluctuating)
B)2) I understand why there are caps on LM7805. Not sure they are necessary
C) Why LM7805 vs. LM340, or LM340A? (vague on the differences)
C)1) More costly: a 5V DC/DC Converter (from CUI) will not present heat dissipation issues
D) Suspect your potentiometer is set too low (the diagram shows a fixed resistor closer to target)

* An isolation transformer helps keep unwanted noise from the system at the cost of voltage regulation. It turns out that voltage regulation is far more important than clean power. The greater the regulation the lower the impedance the better the sound quality.

 

IIonPilgrimg - thank you for the response!
For starters, I'll share the link that has the write-up to the theory behind the circuit...I simply constructed the circuit and gave it a go. I did not come up with the idea for the circuit.

I will say, for the SR5's that require a 5V signal to power the amp, I pull that power from the head unit itself (a 4-pin USB connector: the 4 pin connector side plugs into the back of the head unit and the other end (bare wires) interfaces to the circuit - hence, I do not and have not used the voltage regulator at all. I measured the voltage coming out of that 4 pin port - it's a clean and solid 5V.
Also - I did try to increase the pot to 50K and the call was clear for about 2 minutes then the call turned to garbage.

Hope this write up here answers most of your questions: https://austinnam.blogspot.com/2020/11/toyota-oem-microphone-adapter-for.html

 

Huh... Overseas and about the same chronology as this thread until the original content ceased.

Some comments stick out (amidst a wealth of typical dysfunction):
"The capacity (50 uF) in the upper part is to block DC bias voltage from the aftermarket head unit - some head unit using condenser-type microphone outputs bias voltage from the Mic port, which could damage the factory Mic unit." ('block' means 'absorb/flatten'; '...damage the factory Mic' warrants attention - likely why the OP used a transformer)
"Adding the capacitor to block the DC bias voltage makes a huge difference."
"Some cheap switched mode power supplies have relatively low switching frequency of around 10 kHz, which is in the audible range. So, they may generate a tone noise mixed with the voice captured at the microphone."
"I do seem to hear some more noise/hiss when someone calls me from the car. Any idea what might be causing this?" (and it's response) **
"I didn't use the LM7805 but instead wired up a USB cable and plugged it into a spare USB port on the head unit, and used a 30k Ohm resistor in place of the potentiometer to prevent saturating the amp on the head unit and distorting the audio." (A bad idea - no way to know the 5V origin and risk of inducing a noise loop. 30k Ohm is too low.)

My gut:
The bottom half of the diagram is golden (caps not required though advised *), while the top half wants simplification:
Eliminate the 1:1 transformer and use a fixed resistor on MCO+ (Do NOT cross to MCO-)
50uF cap is worthy of investigation - although I've suffered no ill after a year in operation without it (Kenwood HU)

* Given the simplicity, it is unlikely ACC (or MACC) will ever surge such that LM7805 (LM340) is in any danger of overload or reverse current: ACC (12V) powers only the clock.

** 'noise/hiss' and 'swooshing' sound like descriptions of the same phenomena. (X-ref 'My gut' above)

 

Tonight, I completed a cross-reference table of PIN-OUT data needed to make the CMS functional in both Gen 2.0 and Gen 2.5 Tundra.

With the Maestro harness, one problem is: the black wire supplied at (28-pin J135) pin 18 must be moved to pin 6, because this is ground for MIC 5V+ power (SNS2). [18 is shield and goes nowhere]
The factory MIC will not function without this modification and you will need a tiny little tool to remove it. It looks like this: O--
Soldering (or T-Tapping) CMS to the Maestro harness is then possible. For Gen 2.5 only, the factory harness will require no modification.
Then, the harness can be installed as it would be otherwise and the factory MIC should work, provided the appropriate MIC plug (2.5mm vs 3.5mm) has been selected (depends upon head unit).

shawn474 << you want to try this? (I'll build you one and include my cheat-sheet and one of the pin tools required - you already have a Maestro harness - I forget which Head Unit you have)

 

Was back into my head unit this weekend and have a renewed interest in this.
My Maestro harness has a three-pin orange connector labeled “mic” - would be awesome to use the OEM one and pull out the non-amplified one that I have routed.
I need to re-read through this and figure out what the dealio is

 

Your post about lack of 'two-mics' has renewed my interest also. I thought you were following only from vague interest.
We'll hook you up - in person if need be since we live close-ish.

 

NOTE: THIS ONLY WORKS FOR TOYOTAS (Tundra's too) BUILT FROM 2014 to 2019!

Hi,

I just did this modification for my Android Head Unit (I used an EKIY T7 from Aliexpress) and was successful!. I used the hand drawn wiring diagram from the first post in this thread. The 28 pin plug has five pins dedicated to the OEM Toyota mic. The original EKIY unit has a crappy built-in mic on the front - the mic sound was fairly muted. EKIY actually says to cut off or de-solder the built in mic as it will interfere with the external one. (I consider that a design flaw - as the internal mic should disconnect automatically if anything is plugged into the mic jack in the back of the radio)

My only issue with the hand drawn wiring diagram from the OP was that they put the resister in the wrong spot - it goes in the Mic+ signal wire NOT the 5V+ USB power source. I've watched about 10 Youtube videos where various people say it goes there.

The EKIY Android unit comes with two powered USB cables - one of them is connected to the built in USB - I used the other to power the OEM mic.

I bought a

$10 TWTADE 3PCS 100K Ohm Linear Taper Rotary Potentiometer WH148 B100K 3 Pin with XH2.54-3P Connector Wire Cable + Black Knob Cover Cap 148-100kBK

100K Ohm potentiometer from Amazon so I could easily adjust during testing. While everyone could hear me fine regardless of the setting, many people said I sounded a bit "static" until I adjusted the potentiometer to about 60K Ohm.

You need to use solder/flux/soldering iron because many mic's coat the copper strands with an anti-conductive coating. If you just hand twist and wrap with wire tape, the connection may not be good. The heat from the soldering iron will instantly burn it off.

Please check all connections after you solder with a multi-meter.

Anyway, the OEM mic sounds WAYYYYYY better than the built-in one.

Things I had to buy to do this:

• $26 NuIth 28-Pin Aftermarket Stereo Installation Wire Harness for 2012-2018 Toyota Camry/RAV4/Corolla/4Runner, Add or Retain Reverse Camera/Microphone/AUX/USB/Vehicle Speed Sensor Function
  28-Pin Wire harness (You can get this $10 cheaper on eBay)
• $10 Lavalier Microphone for Rode Wireless GO 2 / ii & DJI Mic Transmitters, Omnidirectional Lapel Lav Videomic with Clip, 5 ft
  3.5 mm Microphone (I lost the one that came with the EKIY head unit)
• I had an extra USB cable, so I re-purposed it for this.
• Solder gun/heat shrink/solder/flux - I had this from a previous project

The following image is official public domain. I release it under Create Commons CC0 1.0 Universal. Do whatever you want with it.

NOTE: ONLY APPLIES TO YEARS 2014 to 2019 WHICH HAD THE 28PIN PLUG

 

What year is your truck, and what radio did it have.
Makes a difference on your pin-outs…

 

Answering what RainMan_PNW asked would help the thread.

You may be the first Gen 2.5 owner to have solved this! Little bit 'long way round' but good to hear the result works.
I am perplexed by your 3-conductor omnidirectional mic (just to cut and discard it) when only a 2-conductor plug is needed for the H.U. (Alpine is 3.5mm)
Using a potentiometer, you landed on approximately the same resistance (62kohm) that works perfectly in my 2008 Gen 2.0. (Did you replace with a resistor - or keep the potentiometer?)
Your USB 5V+ power source is inventive: There is no USB 5V source in a Gen 2.0 Tundra (it must be created from 12V - a USB charge feature could also be created while there)

 

I have a 2016 Toyota Tundra 1794 edition crewmax with the JBL sound system. FYI Toyota Tundra's from 2014 through 2019 all have that same J139 28-pin connector that has the five pins for the OEM mic. Toyota pretty much used the same radio harness on Camry's, Corolla's, Tundras, etc in those years.

I'm pretty happy with the EKIY android unit - Wireless Apple Car Play works great. The only bummer part is that these android units do not natively support SiriusXM - so if I want that, I would have to buy an additional XM-only device and plug it into the radio's aux port. The other minor con is that I miss a dedicated knob to turn change the volume - I have to rely on the steering wheel buttons.

What I do now is use the iPhone/Car Play SiriusXM app, but that's "fake satellite" and just uses the cell phones data plan.

- yup, you are correct - it' was a goof. The original photo showed a 3-conductor mic male jack so that's what I bought - then realized that I only needed two of the wires - so just getting a 2 wire mic - I mean it's like $7 on Amazon so no big deal.

I got the idea to use a potentiometer from some YouTube video - it made sense to me since no one knows what mic impedance Toyota uses in their radios. I spent a few minutes talking to my friend asking them what sounds the best as I slowly increased the ohms. I didn't actually measure the potentiometer - I just turned the knob a little more than half-way - so that's probably 60kohms.

I just soldered the potentiometer permanently into the wire harness and threw it back behind the radio.

There's a guy ITT that says they didn't use any resister but when I set it at 0kohms my friend said they could still understand me, but it sounded like static a bit.

Right, so the Android Head Unit I used has two spare USB connectors in the back for connecting iPods, mp3 usb flash etc - they both supply 5V, so I just used the 2nd one which I wasn't using to power the mic.

 

Reverse of what I meant: When adding a 12V--5V DC/DC (Ex: from cig port, you could also add a 5V charging USB). You've taken 5V from the radio's USB-2 source, in which case a feedback loop may result (unlikely). Also, would question whether the mic will have power without selecting that USB source in the radio?

The real question: Does your setup work?

 

The Android unit comes with two USB ports that originate from the back of the unit. They are designed to be both data transfer and power. They both send out 5V as long as the Unit is powered on. You don't have to select the input on the Android OS. Ultimately it works great. I don't hear any feedback nor does the person I'm talking to.

I normally bought my stuff on Crutchfield, but when wife wanted Car Play (after we rented a car that has it), Crutchfield was like $500 to even think about it with the cheapest radio that supports wireless CarPlay..

To compare:

Crutchfield Radio: Boss Audio BE920 - $249.99 (which is the cheapest crappiest radio)
Crutchfield PAC Wiring Interface including all cables: - $184.00
Crutchfields amazing English-speaking tech support
(note: OEM mic-mod - 28 pin harness $15, potentiometer $10, solder kit $25 )

Aliexpress EKIY C7 Android Unit: $104
Aliexpress Canbus Wiring Interface including all cables: $24.18 (includes cable to use OEM rear camera)
(note: I bought a specific cable to use the OEM GPS antenna for like $6 on eBay - although it's kinda dumb because CarPlay uses the phones GPS, not the cars)
(note: OEM mic-mod - 28 pin harness $15, potentiometer $10, solder kit $25 )
Aliexpress's tech support - they are super responsive regarding tech support questions - you just need to understand that they don't speak native English.

So all in all I spent $175 for the Android unit, vs having to drop $500 for Crutchfield. And even the Crutchfield PAC interface doesn't support your native OEM mic, so you still have to do the mic mod.

With the Android unit, you can go nuts with all of the extra features - for example, you can get front and rear parking sensors, 360 camera, 4G network (though if you use CarPlay, then don't bother), dash cam, tire pressure monitoring, OBD link up - these are about $10 each.

I didn't want to drill holes in the sideview mirrors, and pull cables to get the parking sensors, 360 camera - and I have a stand alone OBD reader, and the vehicle has back up sensors, I already have a dedicated dash cam.

 

Sweet!
You got it working in a Tundra Gen 2.5 (JBL equipped)!
Toyota has used three different factory radio plugs since introducing Tundra and for all I know, a fourth is on the horizon.
To date, there is no such thing as a factory mic adapter. Individual adaptation is the only option no matter the H.U. or Harness you go with.
It can be done but... this project isn't for a wiring novice.

 

There was another poster in this thread that said that all of this was a huge PITA - he just plugged in extra head unit mic, threaded it to just above the sun visor and called it a day. I think I just enjoyed stripping down wires, soldering everything - to me it's kinda a hobby. It bugs me to have a little mic sticking out dangling - so now everyday I tell the wife how cool it looks lol.