baustin wrote:I did replace the original battery with a Bosch AGM battery last fall. That seems to have eliminated the low 12v issues that were causing more frequent fuse pulls. I do not leave the ELM unit connected to the OBD port. I only plug it in to take a reading once a month. The car is plugged in whenever it is not being driven.
Replacing the battery won't eliminate the 12V battery problems - if you have the TCU lockup issue, it just starts the drain on the new battery. Given time, the new battery will start to have problems. That's been reported in this thread early on.
I have left an ELM plugged into the OBDII port almost 4 years without ever having an issue with the 12V. Some people *have* had issues, but I think it is specific to the particular brand/model of ELM being used. I even left the ELM in while I was out of the country for 2 weeks without a problem.
As reported about, leaving the car plugged in when not being driven *can* cause 12V problems. You really don't want to do that.