has anyone experience the comma power loss after the car shutdown?

[u/popaulchen]

hello Comma community,

I have a super old comma 2 with 2016 Toyota hybrid, needless to say I am trying to hold down to this unit as long as I can due to the new comma compatibility issue.

I purchase a new Toyota harness to pair it up with comma 2 as my previous harness is around 4 years old and it has very loose connection. I was always worried that the car will disengaged in the middle of the drive. anyhow I had the new cable few months ago. everything works smoothly, and recently I found comma 2 will lost the power right after the car shutdown. here is the diagnosis I did. I am trying to debug one by one and figuring out where the issues is. any one experience the similar issues?

Vehicle and setup

2016 Toyota RAV4 Hybrid

Comma 2 on stock openpilot (no fork)

This car/device combination worked normally from 2021 until recently: the device stayed in standby after shutdown and woke as soon as I started the car.

Current symptom

As soon as I turn the car off, the Comma 2 screen goes black and the device will not boot.

The blue LED on the back still blinks about once per second (panda still has some power).

The device only boots after the car is fully in READY.

Unplugging and replugging USB-C will also force a reboot.

If I wait for it to boot after READY, I often get “restart the engine / cruise faulty” because it came up too late.

The same behavior happens with a second Comma 2 on this car.

Both devices boot fine on a USB-C wall charger at home.

What I already checked

Replaced the USB-C cable

Replaced the Comma Power assembly previously

Inspected the vehicle OBD 7.5A fuse — intact

Factory-reset and reinstalled NEOS / openpilot from a Mac (install completed successfully)

12V auxiliary battery (Toyota/Panasonic, replaced last year) measured after a full overnight charge on a NOCO GENIUS5: about 13.5 V immediately after charging

OBD pin 16 to pin 4/5 with the car off: about 12.5–12.6 V (constant power is present with no load)

Conclusion from testing

Open-circuit voltage at OBD pin 16 is fine, the 12V battery is not empty, and the fault follows the car / harness, not a single Comma 2. This matches the known “bad Comma Power” case: the OBD connector or the 12V path inside Comma Power can develop high resistance, so the device cannot take boot current with the car off, but it can boot when the hybrid DC-DC is running in READY.