Disabling the DCM (NOT another tin foil thread)

I'm looking to disable the DCM, NOT because I wear a tin foil hat, but simply because my DCM has failed and every time I start the truck I get yelled at "Communication module failed" blah blah blah. I've had it into the dealer twice trying to resolve but the module itself is bad. It's near $2k to replace and I'm not spending that kind of money on something I don't give 2 shits about.

So, my understanding is I can pull the fuse and let the internal battery die, but I'll need to jump some wires for a speaker and the microphone. Speaker is easy enough, but I have a couple questions on the mic.

Am I understanding this diagram correctly?

-On connector D37 at the DCM, I need to jump pins 16 to 6, and pins 32 to 7.
-Pin 5 will no longer be used.

-Pin 23 needs to be grounded? This confuses me. If that connector plugs into the DCM and 23 is a ground, wouldn't that already be grounded elsewhere before reaching the DCM?

-For mic power, we tap into the red wire from pin 5 on the IN1 connector and run that wire to the head unit connector R49, pin 23, correct? Where is this IN1 connector? Does that run to the DCM?

-I've also read conflicting reports that taping into the IN1 harness does not provide consistent power for the mic, has this ever been confirmed?

-Any other issues I might run into with other features by disabling the DCM? With it being faulty I'd think they would have surfaced by now.


** Disabling the DCM by pulling the fuse will disable your factory remote start from your keyfob.

 

I pulled my DCM fuse years ago. It didn't affect the speaker at all. I never talk on the phone while driving so don't care about the mic. I'd say pull the fuse and try living without the mic vs a bunch of wiring gymnastics.

 

What speaker does pulling the fuse disable?

 

I believe it disables the receiving mic in the cab. I pulled the fuse as soon as I took possession of the truck. Now, when I receive a call and it connects via bluetooth, I can hear the caller. But they cannot hear my response.

 

My understanding is if you leave the DCM in place and plugged in it will not disable the speaker because signal still passes through it. I figured I would try just doing the mic portion first and see if the speaker still works fine.

 

Some people claim the passenger dash speaker will be disabled. I had no issues.

 

If you leave the DCM plugged in but just remove the fuse, then the speaker still works because the signal is still passing through the DCM even though it isn't powered on.



For anyone wondering, I completed this today and all worked out, but instead of taping into the IN1 harness (no idea where it is) I just de-pinned the red #5 wire from the DCM connector and extended it to the head unit R49 connector.
If anyone is looking for info on how to do this and doesn't want to dig through multiple other threads and pages, here ya go. Note: de-pinning is a bitch because toyota uses tiny pins. Good luck!

Pull the DCM fuse from the underhood fuse box.
Locate DCM. On my 2020 it's behind the glove box. Look for the module with 3 large coax cables running to it. It was farthest to the right in my truck. The network ECU was either not present or not close enough to see it.

 

Just to answer some of your unknowns:
IN1 is midway up the driver's side A-Piller, must remove the plastic trim, IN2 is also located there. Where you performed the work is a better location.
The Network Gateway is located above the large tube above the modules and more rearward. I had only just found it today too.

 

Thanks a ton for posting this information @2one8! The jumps on D37 and the connection to D49 make sense, but did you end up jumping the speaker wires on D38 as well? From what I thought I understood, that step wasn't needed as long as the DCM was still connected but unpowered?

 

I jumped the speaker wires simply because it was stupid easy to do and I already had jumpers made from another project. But yes, my understanding is if you leave the speaker connector plugged in it will still pass the signal even if the DCM is powered off.

 

Wow, thanks for posting what you figured out!

as far as jumpers, did you use something readymade, or you made your own jumpers, cause nothing fit?
Curious what your jumpers over the tiny pins look like, if you took a pic or ever have the area open again. And yes i know, for my case i probably won’t need any jumpers at all, and that a jumper can just be a piece of wire and there might be a number of ways to make one, but sometimes it’s nice to see how someone did it easier/simpler/neater without screwing up or jumping/shorting anything undesirable.


So once the DCM fuse is pulled, the DCM battery should die, and if you want, you could also unplug the thing with the phone button and light, part of the centered plastic thing that pops into the roof/headliner area, and the right speakers won’t yell “communicAtion module failure detected, please contact your dealer”, because the part that plays the recording about communication module failure will have no power …. ?

 

This is so helpful. Thank you!

Question for anyone on Tacomaworld: Does anyone have any recommended jumper wires? I have not opened things up yet to see how small the connections are, but from what I've read, they are pretty small. I'm not sure my original plan of using speaker wires is a good one.

 

For the speakers I used male pins from this kit. They fit perfectly:

$28 Twippo 708Pcs Waterproof Automotive Electrical Connector Terminals Wire Connector Plug Kit 1/2/3/4/5/6 Pin (43Sets)

https://www.amazon.com/Twippo-Water...8-3-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&th=1

For the rest of them I'm unsure what to use. The male pins are tiny, probably around .010 to .020 thick. I did not have anything in any of my connector kits that were small enough, I tried soldering the end of the wire but it was too thick, so I ended up disassembling the connectors and removing the pins from the connector, and then heat shrinked the ends together. This way I can cut the the shrink and reseat the pins if I ever want to reverse it all. I suppose a guy could use a small enough needle and solder the wire to the needle.

 

See my reply above regarding jumpers and such.

Once you pull the fuse I don't believe the speakers will yell at you anymore. If they do it should stop once that battery dies. Theres no need to do anything in the headliner.

 

Update:

It appears disabling the DCM also disables the factory remote start when using the keyfob. I haven't tested by putting the DCM fuse back in, but disabling it is the only change I have made since the last time it worked that may affect it.

 

Yep just tried mine and it doesn't work. That sucks

 

The factory one is garbage and I plan to put an aftermarket one in anyways

 

Verified also. Pin 30, beige wire, of the large connector on the DCM seems to be the culprit. De-pining it also disables the remote start. During a proper remote start operation the line is brought close to ground.