Disabling the DCM: A How To

Hello Tundras.com

I have been on a journey to disable to the DCM in my Tundra for a year+ now and I believe I have a fairly clean solution. This write up is a summary of why and how I did it that I hope will be helpful to any others who wish to do this.

What is the DCM?
DCM stands for Data Communications Module. It is the device that receives and transmits over-the-air telematics to and from Toyota. All Toyota Connected Services depend on the DCM module including Safety Connect, Service Connect, Drive Connect, Remote Connect and Wi-Fi Connect. Back in 2018, Toyota outlined for customers and shareholders its vision of a fully networked fleet of cars where each Toyota vehicle transmitted data to Toyota corporate who then shared it with dealers, insurers, and, if needed, emergency services. The modern DCM module is the realization of that plan. You can read more about it from Toyota here. Below is an infographic that gets you the rough idea.



Why would you want to disable the DCM?
There are many reasons to disable the DCM, but some key ones include:

• Constant data transmission: The DCM is an always-on cellular connection that continuously sends data to Toyota's servers. You can call Toyota and opt out of Connected Services, but your DCM is still active and you have to take it on faith that it's no longer transmitting anything.
• Sale of driving behavior data: Car manufacturers sell your driving data to third parties, including data brokers and insurance companies, often without clear consent. Here is an article on how GM, Honda, and Hyundai did this and here is an article about a lawsuit alleging that Toyota has done it. There are many, many more articles available on Google detailing how all auto manufacturers sell your data.
• Data vulnerability and other security concerns: Companies are not good stewards of your data and they frequently lose your information through hacks, leaks, and other means. Beyond that, there is the ever-present possibility of bad actors gaining some level of control of your vehicle through its connected services. Car manufactures supposedly work to keep this from happening, but anything connected to the internet is more vulnerable than something that isn't. Here is a Wired article discussing this issue.
• Government and police access: Automakers have been known to provide law enforcement with access to vehicle data without a warrant. A recent Senate investigation found that despite public pledges, most car manufacturers share your data with law enforcement without a warrant - including Toyota. Read more here.

Finally, I hold that we have all paid tens of thousands of dollars for our trucks and the data generated by our driving behavior should belong to us, not to insurers, Toyota corporate, or anyone else.

Why would you NOT want to disable the DCM?
Despite what I've outlined above, there are reasons to keep the DCM functional in your truck. The most important is that if you disable the DCM, you will lose access to the Connected Services, including and especially Safety Connect. Again, if you disable the DCM, you will not be able to use your truck's call button in an emergency. If your truck is stolen, Toyota corporate will not able able to track it down for you. You won't be able to use the AT&T wifi. Your dealer won't be able to pester you for an oil change.

Is disabling the DCM just for the tin foil hat crowd?
No. See my reasons above, none of which have anything to do with tinfoil hats. Also, remember that tinfoil hats make it easier, not harder for them to read your mind.

How to disable the DCM
So, you've decided to disable the DCM, but you are not sure where to start. Let me outline my process and why I selected this one. Note that everything below applies to a 2.5 gen Tundra with a DCM installed. It may work for 3rd gens, but I am not sure. Finally, note that any modifications you make are at your own risk. I make no guarantees and you assume any risks associated with voluntarily modifying your truck.

Note: To access the DCM, you will have to take apart the dash. There are lots of guides on this, but I'm partial to this video prepared by NitroZ18 Fishing here.

DCM Location
The DCM module is located on the right passenger side behind the glove box.

(credit to @1lowlife from this thread for the image)

Here is a close up image I took. The DCM is the box with the blue, gray, and white antenna cables running into it.



Method 1: Pull the DCM fuse and live without the in-car microphone.
The easiest and cheapest way to disable the DCM is to pull the DCM fuse and. You can find the appropriate fuse on the driver's side below the steering wheel. Here is a fuse diagram to help you find the correct one.


(again, credit to @1lowlife from this thread for the image)

The downside of this method is that if you pull the fuse, you will lose access to the OEM microphone. Yes, that's right. For unknown reasons - and maybe out of spite - Toyota runs your truck's microphone connection through the DCM. A solution might be installing an aftermarket head unit and microphone, but for those of us committed to staying as OEM as possible, see method 2.

Method 2: Bypass the microphone and unplug the DCM
The next method is jumping the microphone connection and unplugging the DCM. This disables the DCM and leaves the OEM microphone intact. Some of your are probably handy enough with electronics to make the jump yourself, but for those of us who prefer something plug and play, AutoHarnessHouse.com has a bypass kit for $90. You can find it here.


Credit: AutoHarnessHouse.com

All you need to do is access your DCM module and unplug the gray and white connections, then add the bypass modules from AutoHarnessHouse.com. Here is a picture of my bypassed cables.



Zip tie everything down to avoid rattles, reassemble the dash, and you should be good to go. The final tests are to see if your head unit displays the DCM notification or not and and if your microphone still works.


Look Ma, no DCM!

Note: I found this method thanks to madmax2 over at Tacomaworld.com and I give full credit to him for pointing me in the right direction. You can find his write up on post #318 here.

Conclusion and final wrap up
Anyway, I hope this is helpful for anyone looking to disable the DCM.

Credits and references
My DCM disconnection odyssey
Disabling DCM telematics transceiver “safety connect” connected services module)
Simpler solution for disabling the DCM telematics - Silencing Antennas

 

Do you have any more pics of the grey connector to bypass for the microphone? IE pins and which wires you have to jump?

 

Apologies, I should have taken more thorough pictures of that before closing everything up, but did not do so. Here is the best close up of the gray connection that I have.



That said guaco.supreme over at tacomaworld gave instructiosn for how to jump the DCM in 3rd Gen Tacoma. I believe his instructions would be the same for a 2nd Gen Tundra. For your reference, I'm going to drop his diagrams below. That said, see his full write up on beginning on post #7 of this thread linked here.



Credit: guaco.supreme at Tacomaworld


Credit: guaco.supreme at Tacomaworld