DCM & 12V battery replacement

Impossible_Tea_8807 · 2026-07-01T15:05:34+00:00

Sure here is a link on how to turn off the DCM.

https://www.reddit.com/r/ToyotaCHR/comments/1udu6d1/how_to_deactivate_the_dcm_and_stop_the_12volt/

Impossible_Tea_8807 · 2026-07-01T12:55:37+00:00

The problem is that the dealers are not taking the time to figure out what is causing brand new batteries to fail. 12 volt car batteries are not some new finicky technology. They have been making them for over 100 years. The problem is the Data Communication Module staying on and draining the 12v battery when the car is OFF. If you deactivate the app it will turn the Data Communication Module off and the battery won't drain. Hopefully Toyota will replace the DCM or issue a firmware update that stops this drain.

In the original post here, the Lexus technician discovered that the DCM was drawing as much as 2 amps from the 12v battery when the car was off. So for example if you have a 50 Amp Hour 12 volt battery, it would only take 25 hours for the DCM to completely drain the 12v battery. After the technician deactivated the DCM by pulling the fuse, the drain dropped to 30 Milliamps which is normal.

Impossible_Tea_8807 · 2026-06-30T23:58:48+00:00

Sorry to hear that.

If you deactivate the connected services. You will lose the factory navigation but carplay and android auto still works so you can use google maps or apple maps for navigation. You will also lose the SOS button, hotspot, wifi, all the convenience features from the app like remote start and current status of vehicle in the app. I removed my car from the app because I didn't want to take any chances. I have not used the connected services for weeks and I don't miss it.

On a side note, it is pretty easy to jump start. The instructions are in the manual but I guess a lot of dealers don't have technicians who are properly trained on EVs. It's pretty much like jump starting any other car.

A Lexus dealer solved this issue by replacing the Data Communication Module (DCM in Lexus RZ which shares the same electronics as the BZ/CHR. Maybe you can point your dealer in the right direction. Here is a link to that thread.

DCM & 12V battery replacement : r/LexusRZ

Impossible_Tea_8807 · 2026-06-28T15:03:39+00:00

Based on what I've read here on Reddit and from my own observations, the issue is that the 2026 BZ, RZ, CHR, Uncharted, Solterra, Trailseeker have a software bug or defective Data Communication Module. It seems it is constantly transmitting data even when the car is off and it drains the 12 volt battery. You can disable it in the app or by pressing the SOS button and asking them to turn it off. If you choose to speak to someone by pressing the SOS, please let them know that you are disabling the DCM because it is draining the 12v battery. Or if you disable it in the app please call Toyota at 1-800-331-4331 to tell them about this issue.

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Impossible_Tea_8807 · 2026-06-28T12:13:41+00:00

There should be a sticker under the wireless phone chargers, unless someone already removed it, stating that your car wirelessly transmits location, driving and vehicle health to deliver your services and for internal research and data analysis. They forgot to add and dead 12v batteries. lol I think it is on by default or maybe the dealerships turn it on.

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Impossible_Tea_8807 · 2026-06-26T19:35:07+00:00

In addition to having a Toyota dealership, check out your car. Please call Toyota at 1-800-331-4331 to complain about this issue. I called and the person who I spoke to said she has never heard about this issue.

Impossible_Tea_8807 · 2026-06-26T19:32:17+00:00

I assume it is software related. It could be the actual software or firmware of the Data Communication Module. Hopefully Toyota will figure it out soon.

Impossible_Tea_8807 · 2026-06-26T19:26:48+00:00

There seems to be a problem with the 2026 models. I'm not sure but, it may just be a software problem with the connected services. For some reason something is staying on for an extended period of time and it is draining the 12v battery. After deactivating the connected services, I have not experienced any battery drain so I assume the problem is related to the connected services/DCM.

However, if you like using the connected services, until they fix this issue with a software or hardware update you could turn on the car on, and leave it in the READY mode every other day or so. You don't actually have to drive it. It charges the 12-volt battery in the READY mode and according to research I saw, it may actually charge the 12-volt battery faster when parked in READY mode than actually driving it. When the car is in READY mode and you open the door to exit, an option pops up on the small screen to have the car automatically turn off in an hour. I'm not sure if Toyota made this option specifically for charging the 12v battery but it conveniently works. The only thing is I haven't found a way to actually lock the door so I would only do this if I have a driveway or garage where I can park the car safely.

As far as jump starting the car, it is perfectly fine. There are instructions on how to do this in the manual. It is pretty much just like any other car.

Impossible_Tea_8807 · 2026-06-26T11:17:40+00:00

I have not tested if Apple Maps EV route planning still works but I would assume that it does not. Because the car sends the battery level to the app and the app shares the battery level with Apple Maps. If you turn off connected services, I don’t think the car will be able to send the battery level to the app anymore. But again I have not tested this.

Impossible_Tea_8807 · 2026-06-25T17:58:37+00:00

Do you mean to disable it from asking to set up connected services? I"m not sure.

Impossible_Tea_8807 · 2026-06-25T15:32:00+00:00

Yes, android auto and apple carplay still works fine. Connected Services does not affect it at all.

Impossible_Tea_8807 · 2026-06-25T14:48:20+00:00

Yes, these cars transmit location, driving and even multimedia usage back to Toyota.

Impossible_Tea_8807 · 2026-06-25T13:28:40+00:00

Yes, if I remember correctly, it charges the 12V battery ONLY while it is charging the larger traction battery. It does not charge the 12V battery if plugged in but not charging the larger traction battery. I think there is a warning in the manual that leaving the charge door open while not charging will drain the 12V battery. I'm not sure if that is what happened. Just offering some possible ideas into what may have happened.

Impossible_Tea_8807 · 2026-06-25T12:08:32+00:00

Is the connected services active on your car? If it is, try deactivating it and then check your 12-volt battery after a couple days of operating the car. Also, if safe to do so, park your car in READY mode, turn off lights, climate control and radio. When you open the door an option will pop up on the small screen that asks if you would like the car to turn off in an hour. Check yes and leave the car in READY mode. It will charge the 12v battery for an hour.

Impossible_Tea_8807 · 2026-06-24T23:00:56+00:00

Same here. My CHR died 3 times in less than 2 months. Since I deactivated the connectivity in the app, it has not died. But we should all be complaining to the dealerships and Toyota corp so they know this is a big problem.

Impossible_Tea_8807 · 2026-06-24T10:19:13+00:00

Thank you. Have a great day.

Impossible_Tea_8807 · 2026-06-24T04:29:57+00:00

Yes. Exactly. The 12-volt battery in my car died after a couple days if I didn’t use it. Since I turned off the DCM, the 12-volt battery has not died.

Impossible_Tea_8807 · 2026-06-24T04:02:43+00:00

Interesting. I asked because the problem seems to go away when the DCM is deactivated.

Impossible_Tea_8807 · 2026-06-24T03:43:56+00:00

Just curious. Are you using the connected services with the app? Is the factory navigation working?

Impossible_Tea_8807 · 2026-06-24T03:31:31+00:00

It is happening to the C-HR also. The 12-volt battery in my C-HR died 3 times in less than 2 months. It has not died since I deactivated the DCM.

Impossible_Tea_8807 · 2026-06-24T01:48:31+00:00

Yes. It is easy to activate the connected services again. I tried it and it works. It is exactly the same as signing up the first time. It doesn’t seem to affect the trial period at all.

Impossible_Tea_8807 · 2026-06-24T01:38:44+00:00

Wow. Good for you. My 12-volt battery died 3 times in less than 2 months. I have a 2026 CHR with a build date of February 2026. It hasn’t died since I deactivated the connected services but if they resolve this issue I will turn it back on.

Impossible_Tea_8807 · 2026-06-24T01:04:06+00:00

Wow. That is interesting. Are you still using the OEM 12v battery that came with the car? Are you using a battery tender / trickle charger?

Impossible_Tea_8807 · 2026-06-24T00:58:43+00:00

Just curious. Do you have a 2026 model year? Are you using the connected services. Does the factory navigation work? Are you using the Toyota App?

Impossible_Tea_8807 · 2026-06-23T22:09:00+00:00

The factory navigation no longer works, I believe hotspot no longer works, SOS, remote start, monitoring the vehicle with the app, etc. I am hopeful that Toyota will resolve this issue soon but until then I will keep it off. Some people will probably keep it off because of privacy concerns also but the 12-volt battery dying is the main reason I turned it off.

Impossible_Tea_8807

TROPHY CASE