My DCM disconnection odyssey.

So question. I know the DCM can be completely taken out with the two by-pass cables and maybe I missed it somewhere, but what do those hefty cables (circled in red) do?

 

Look here.

https://www.tacomaworld.com/threads...the-dcm-telematics-silencing-antennas.821649/

 

Recent related article regarding security flaws with automotive software: https://techcrunch.com/2025/08/10/s...ne-hacker-remotely-unlock-cars-from-anywhere/

 

I’m thinking of buying this and trying it with my Accesorides Takeover remote start. It sounds like it will work… just hoping the experience I have is the same. I’m tired of smart connected devices (especially for a vehicle like the 4Runner… if I wanted a Tesla, I’d get a Tesla).

 

Post pics of how you connect it if you get it to work together. I'll probably mess with it in the fall when it's cooler and I have more spare time.

 

Question: did you lose any functions when you disconnected all of the connectors that were plugged into the DCM?

I just ordered the harness and plan on installing this weekend. Looking at the instructions @madmax20 gave, I see only 2 connectors get plugged into the bypass harness. I was wondering what the other connectors below do.

I hate working with trim panels so I’d like to have this install be a one and done thing.

 

Do you know what the connectors (other than the two that connect to the bypass harness) to the DCM do? I got the bypass harness in today, and will probably try to get this done this weekend. I'm thinking of removing the entire DCM module, but can't find any answers to what those connectors do. I did look through the thread on Tacoma world that Captain Spaulding linked to, but most of it is way over my head. From my understanding it looks like they were making a DIY version of the bypass harness, but I'm probably wrong.

 

I believe that those 3 connectors all go to the shark fin antenna on the roof. One is a GPS antenna (for the GPS inside the DCM. The nav system has its own antenna.) one is the DCM cellular antenna, and one is the DCM WiFi antenna. You can unplug them or leave them connected. Won’t matter once you install the bypass cable. The DCM might work for a short time until the mayday battery runs out but the the DCM will be dead.

 

Next thread:
How does Google maps know traffic patterns and how can I opt out

 

I have a nice pocket sundial that not only tells the time, it will also align with north south whenever you get a time reading. Two fer one!!! Navigation might be a little slower if it’s cloudy out, (since you’ll have to wait till it’s not…), but it’s probably the surest way to opt out.

 

Nice! Are the instructions in Latin?

 

Unfortunately no. The manual was in chinglish, and the pages were all out of order, but I figured it out lol. Tells time to the minute!!! But you have to account for daylight savings time on your own.

What’s nice is that if you get amnesia for an undetermined amount of time on an uninhabited island , but you roughly guess the time, you can work backwards and get a pretty good approximation of the month/date as well. As long as you know your latitude.

Isn’t modern tech great? Now I don’t need my phone for anything!!!

 

Ok I just did the bypass harness install. Unfortunately it looks like one of the connectors they sent me is defective because my microphone is not working at all. Everything else is good. I emailed them to see if I could get it exchanged.

ETA: they replied instantly with a tracking number for a replacement.

 

First post here with a quick question, but first here is my own little odyssey..... I bought the bypass harness for my 2019 4R SR5 Premium, but when I reached the spot where it's supposed to be (very easily per description by madmax20, thank you very much, and also as shown in my 2019 factory manual) there was no DCM at all! So, now I'm feeling pretty dumb and emailed Auto Harness House and they replied that only 2019 models with a JBL system had it installed. Ok, so much for that, I suppose, I hope I can return the harness or maybe I'll sell it to someone else and wrap it up.

Now the question now is: is there a DCM at all in my vehicle or is there a DCM function that's maybe incorporated with some other component in my year model? As I understand the DCM function is alive in many Toyotas as early as 2010 or so, but where and how? Thank you all for any input.

Just for fun, following is a pic I took of the empty bracket

 

Welcome to the forum.

I have a copy of the 2010 4Runner wiring diagram and the DCM is included in that document. So we know the DCM was being put into cars as early as 2010. According to this press release Toyota expanded its inclusion of the DCM across more models and trims in 2017.

Whether or not your other Toyotas have the DCM I do not know. Certainly if your car has an SOS button, any connected services, or remote start from the Toyota app it will have a DCM. There may be models that have the DCM that offer no such user interaction. Premium stereo or a factory Nav system might also be indicators. As far as non Toyota vehicles having some version of a DCM, the newer it is, the more likely it is.

 

The issue is not DCM, but that version of DCM found in 2019+ 4Runner models used to collect and send usage and location data to Toyota. It does so using built-in cell modem.

For pre-2019 trucks, I recommend checking p/n of your DCM to ensure it is one that contains cell modem. Indirectly, if you have SOS button then you also have cell modem equipped DCM.

 

Why do you think that there are DCMs without cellular modems? Not trying to be snarky. Just asking.

 

Would the early DCM's even work anymore? I'd be willing to bet they used a 3G signal and most of those networks have been deactivated by all the carriers

 

It may be possible that data can be transferred via a connected cell phone. The multimedia manual is a little confusing on this point.

 

Thank you for all your info, Capt Spalding.

My 2019, according to Auto Harness House, must have never had a DCM at all... and that's just as well with me; and also being a good company, they kindly approved the return of the bypass harness I had bought.

 

Indeed, I read somewhere that previous 3G versions of the DCM stopped being supported by Toyota, regardless of subscription, on November 1, 2022. Although this doesn't 100% mean that data isn't collected any longer. But in my case the module was actually never there

 

I wonder if you'd be willing to show us a picture of your radio when it's on.
If the car is equipped with A DCM it will usually say DCM on the top right corner of the radio. Along with the signal bars.

 

Don't mind sharing at all; been grateful of all the good info here. Today or tomorrow, I'll put everything back together (been driving my trusty 1998 CRV in the meantime so I was in no rush to close up the dash until I'm quite sure I don't have any other business back there..) and will check the screen and take a pic when I reconnect the battery.
I'm not done with my research anyway; I'm still trying to figure out if my July 2019 4R is transmitting data from somewhere else and if so, from where and if it can be interrupted without mucking up something else. This year model may not have the DCM indicator, as connect service would not have been on demand, I don't think, just automatically enabled for Toyota's/others purposes. The manual seems to indicate, for example, that in a crash an emergency call with location will be made

 

Cost of parts and cell service in 2010.

 

So what would the means of communication be for the digital communication module if not for cell service? BTW, OnStar has been using cell service since 1997.

 

Britus,
There is a possibility you are looking in the wrong place.
Earlier 4runners placed the DCM on the left side of the driver as opposed to where my instructions point to.
Take a look at this youtube short.
https://www.youtube.com/shorts/0ER9ZA0tIT8

I'm just putting the possibility out there.
Best of luck to you.

 

Hello Madmax20, here are photos that were convincing me that my 4R doesn't have a DCM until I saw your last message: no DCM on screen, no manual SOS switch and no fuse called "Mayday" in the fuse box

 

But now, I must re-look at the whole thing again and will be pursuing the potential for a different location for the device. Thanks for following up, luckily I really don't mind getting to know my 4R better....

 

Hi Britus,
Thanks for sharing. Right, no DCM on the radio, no red SOS button in the dome panel.
You might just be safe after all.
...
Just one more thing, (holding a cigar like Columbo)... The DCM fuse (if there is one) is in the in cab fuse box below and to the left of the steering wheel.
Good luck!

 

If you listen closely to the video he refers to the DCM 12v wire where it connects to the BCM, or Body Control Module. The component he removes in the video is the BCM.