DCM disconnect

This is for anyone interested in stopping outgoing communication from the DCM.

As you can read in the linked threads below if you choose to read them in full, plenty of unsuccessful attempts were made across generations and models. None were simple or definitive, some caused speakers and microphones to stop working, as well as incompletely stopping all outgoing transmission. Then user @madmax20 contacted Autoharnesshouse who made a solution. This will apparently stop all outgoing communication from the DCM/telematics module. It is possible or even likely this will deactivate some or all of Toyota’s connected services, but I’m not using them so can’t comment. Notably remote start requires connected services so it won't work. The company makes this point on their website.

As for why, I simply prefer to reduce giving companies free information about me when possible. And I have no need for the services Toyota provides in exchange for the information. For those who will argue that since x other device (i.e. phone) sends information to y other company anyway so it’s worthless to even try to limit personal data shared with any company, I’ll just say I disagree with that black and white philosophy of life. I try to limit it when possible and know it’s impossible to live in the modern technological world without inadvertently providing some personal data to companies. I have nothing against those who don't have this concern.

I have no relationship with the company who produces these; I simply emailed them to ask if this would work on the 4th gen and they promptly responded yes after looking at the schematics. I paid full price.

I installed it just tonight and drove about 15 miles back and forth to the grocery store afterwards. There were no new warning lights, beeps or other alerts. Everything I use worked perfectly. The truck drives exactly as it did before.

Links below for the harness, and the threads which led up to the solution.

Harness:

• Toyota DCM/Safety Connect Bypass Harness - Fits 2020+ Toyota Vehicles

Threads preceding the solution, with detail in the TW thread describing how prior attempts did not completely stop all outgoing communication, as demonstrated by @Disgruntled Scientist. I contributed to exactly zero of them.

• My DCM disconnection odyssey. | Page 9 | Toyota 4Runner Forum [4Runners.com]
  
  
• Simpler solution for disabling the DCM telematics - Silencing Antennas | Page 18 | Tacoma World
  
  
• .

Installation:
I did not disconnect the battery. You should because that's generally recommended when doing anything on electronics.

Cover behind the shifter pulls off if you slip something pointy and skinny around the edges and just pull.


You're detaching the plugs which contain 1-the two bundles of colored wires to the right, and 2-the one bundle of colored wires in the middle.

The plugs disconnected


The harnesses attached to the plugs. Then just tuck them back in behind and replace the cover you removed.

 

Does this affect OTA updates?

 

Not sure if WiFi is part of DCM or on in the headunit itself. If it's in the head unit you probably could do OTA updates over WiFi, but the vehicle could theoretically still upload any stored data at that time.

USB-based updates should still be available: https://www.toyota.com/firmware-updates So far there aren't any for 4th gens.

 

CarPlay works and WiFi has some role in that.

 

@OP: I'm not currently inclined to do this myself, but wanted to give kudos for a great post.

 

@Thegreatgretz This is even better than blinding the antennas. Unpower the DCM completely! Thanks for sharing this info.

 

Particularly since we don't know the long term affects of the DCM not being able to call out.

I bring this up because there have been cases of modules like that getting very upset when they can't call out. For instance, Subaru had this issue a few years ago. Their communication modules used 3G cellular networks to call out. 3G has since been EOL'd. The modules see no signal and crank their amplifiers' gain all the way up to try and grope for a connection. They try to do this even when the car is off, as the modules are used for the emergency call out system that can call out in the event of a crash. Normally, they're powered by their own lithium ion battery. Problem is, between age and being sucked dry by the now prolific power requirements of the communication module, that battery wears out. When that battery is low, the module's charging circuitry draws from the main battery. It doesn't draw a ton of power, but it's enough that it can run your battery out over several days and then your car won't start. Even worse, the added strain on the main battery from this behavior kills it prematurely, so you often need a new battery, too. You can't just unhook the DCM, as it controls the microphones, so you lose the ability to do calls with a paired phone.

There's an update you can get from Subaru that disables the 3G modem, but you usually find out about it after everything has already gone to hell. Since Toyota and Subaru have a lot of overlap in their electronics, I worry Toyota might have the same problems in the future. Time will tell, I guess.

 

Very interesting observations; thanks for the broader context. I can't answer any of the good questions you raise, specifically if this harness eliminates all power draw pathways from the battery. This sounds like a job for @caribe makaira who as far as I can tell is the local electronics guru, with TIS access and mad crazy wiring wisdom. Or perhaps for the harness manufacturer. My ignorance here prevents any useful contribution.

In the interim, I'll keep an eye on my starting battery voltage after I hunker down at home a few days without leaving or starting the truck, which is not a rare occurrence.