[Moonburn]

I lost power last year. Car was able to crawl to my office. Messages, "Loss of propulsion, reduced power", "loss of steering assist". Later I drove it the dealer and it seemed OK, but had the check engine light on.
I had an OBDII plugged in at the time. The dealer replaced a module behind the brake cylinder

I read somewhere that someone else had the same problem and they wondered if the OBDII had any role in this.
I decided to only plug it in when I wanted data.

Last week I plugged it in and forgot about it. This morning I started to back out of the garage and I had no power steering. I decided to drive it a bit and see what else was amiss. I then got the loss of propulsion message, the traction control off icon came on, check engine icon, and loss of steering assist message came up. I stopped the car, pulled the OBDII, did a reset of the infotainment system. Everything then seemed back to normal. Even the check engine icon went out after driving 20 miles.

Weird, huh?

 

[Sean Nelson]

Weird, huh?

The OBD connector taps into the car's communication bus. If a reader floods the bus with requests for codes then it could potentially preempt some important messages from going through. Or it could be as simple as poor circuit design or manufacture in the reader causing noise on the bus.

 

[GJETSON]

I mentioned that my TPMS failed to relearn, and I couldn't clear the fault message from the DIC to try again. Tried everything I could think of, including pulling 12 volt power to reboot the car. Nothing worked until I drove to the dealer. They were able to clear the DIC first try. The only change was that I had removed the OBD2 on my way there.

 

[drdiesel1]

Those plug-in devices can/will/do interfere with the vehicles communications.
They will cause issues. Then the owner blames the car, removes the device
and takes it to the dealer to have warranty work done. Never tells the dealer
about the pile of junk they have hooked to the cars can-bus system.

Then, they wonder why the dealer can't find the problem and needs to keep the
car for a week while they try to duplicate the problem, without being able to.
I keep telling people, but, they all know better. You get what you deserve, IMO!