Getting Toyota's DCM Talking Again

Toyota Camry XSE Curves

Every new Toyota vehicle comes with Toyota Care – which is a combination of a no cost maintenance plan for two years or 25,000 miles; along with two years of road side assistance. I have had Mach 5 since the end of March but because of the pandemic, she hasn’t gotten many miles. So, when I rolled up to Piercey Toyota for my six-month/5,000 mile service appointment, I had just short of 750 miles on the odometer. It wasn’t that I needed the appointment for the check up, but it was good to take advantage of the free service.

What I did go in specifically for was to get the DCM (Data Communications Module) and head unit fixed. The car stopped sending and receiving data sometime in May and it never recovered. The data sent includes where I last parked and the status of the car (mileage on odometer, fuel level, if doors/windows/moonroof/hood/trunk are opened/unlocked, etc). It is also the data path for remote starting the car and remote locking/unlocking the vehicle. And lastly, it is how the vehicle gets firmware upgrades.

There are lots of complaints about Toyota vehicles losing connection to the Toyota Connected Services. From what I can tell, it is because the head unit loses connection with the DCM and the head unit has no idea that the connection is severed – it keeps dumping data into a blackhole. The only solution is to reboot the vehicle (not joking): Disconnect the car battery and leave it for half an hour, then connect it back up again. That reboots the DCM system and it everything is hunky dory – but, eventually it will all fail again.

If you’re reading this and your Toyota app no longer talks with your Toyota vehicle, it is the vehicle and not the app that is the issue. If the dealer tells you different, then you should challenge them because they either don’t know about the issue or they are not being honest about it.

In March 2020, Toyota put out a Technical Service Bulletin T-SB-0021-20 with guidelines on how to install a new low-level firmware which would resolve this connection issue. The upgrade cannot be done OTA and has to be done by a Toyota technician. The bulletin reads:

Some 2020 model year Camry, Camry Hybrid, Corolla Hatchback, RAV4, and RAV4 Hybrid vehicles may exhibit a condition in which the Remote Connect app does not accept the activation code and/or becomes inoperative, and/or the SOS call center does not receive the vehicle’s location data in a timely manner. Follow the Firmware Update Procedure in this bulletin to address these conditions.

Because of shelter-in-place, I was in no rush to get this done earlier – and that is why I waited until this first service appointment to have Toyota complete this upgrade.

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A few minutes before I got notified that Mach 5 was ready for pick up, my Toyota app pinged me with a message that all the doors were unlocked and opening the app showed me that Mach 5 was parked at Piercey Toyota (instead of a Costco in South San Jose).

The paperwork that I got from the technician says that they upgraded the software:

Customer states that the head unit is not connecting to the app and found out that the unit has an update. Please check and perform update if available. Verified and confirmed customer concern, disconnected battery, reset radio system, deleted personal data. Updated the head unit as needed.

There is no way that I can verify that the upgrade was actually performed or if the technician only did a “reboot” of the DCM. I will wait and see if the issue has been resolved, but that will take time – I will update this posting in the future. There are some positive reports that this software upgrade does cure the connetion issues, so I am hopeful.

I was initially disappointed that they reset the personal data, but since I use Apple CarPlay, the only thing I really needed to do was get Mach 5 connected with my iPhone 11 Pro again.


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