I have a 2013 Mazda 3 with a parasitic battery drain. Before the drain started, the Bose system radio started to turn on and off by itself. A few weeks after that started, the battery started draining overnight. I had a radio shop look at the radio, and they told me the radio was bad, and was the cause of the battery drain. They disconnected the radio and the drain seemed to disappear...but it resurfaced a week later. This time, it would take 3-4 days for the battery to die instead of overnight. So, I took it in to an automotive engine shop that does electronic work. They pulled all fuses and narrowed it down to one circuit, then to one wire in the circuit located under the dash. When they disconnect that wire, the drain stops...but they don't know what the wire connects to because everything operates properly on the car with that wire disconnected! They're now thinking that the offending wire may run to something on the car that controls something that doesn't exist like an option that was never installed when the car was built...but they aren't sure.

They gave me two options for what they could do. The first, which is what they recommend, is to disconnect the problem wire and take the car for a thorough drive to see if everything operates properly on the car. That would sort of a solution to the battery drain. The other option is to remove the entire harness containing the problem wire and chase it to its source. The second option would be VERY expensive to the tune of $1500 or more. They also said that, when new fuses were installed for the radio and it was reconnected, it still didn't work, so the radio does seem to be bad but doesn't seem to be related to the problem with the mystery wire/controller they found. Does anyone here have any advice?

 

I can say without a doubt that if disconnecting the wire fixed the problem, there is no need to fish around for something more. I took my car in to replace struts and now my parasitic drain is a problem. I have a Mazda 3, no problems ever, now this. I'm taking it to a place like O'Reilly's, or such as advance auto, not a plug for them, and see what codes come up. They check for free so they won't lie. They make nothing for it. You probably already fixed this, but wanted you to see this list. My new mechanic did all these things. I've had mechanics do all kinds of things to my car for a buck. I will be complaining to mechanic and telling him to fix it free or I will make it public.
if-your-mechanic-tells-you-these-things-look-for-another-mechanic.html

 

*****... what can I say, go find a competent service shop. I am mean really those guys can't read a wiring schematic?
And on an ECU controlled vehicle you DON"T pull all the fuses to find a battery drain!

The problem was NOT SOLVED
Wow the start of a new week I get entertained first thing on my favorite forum.
Tjocean do you tell your doctor that as well? LOL

As for a "FREE" Diagnostic code check from O'Reilly's, keep in mind almost all employees are NOT by any means trained for diagnostic work. Also getting a DTC is only the start of the long process for resolving an issue. So if you get a P0300 what are "you" going to do? LOL
That my freind is a joke because that is one of the most common DTC that are retrieved and is a generic TC that could be almost anything generating it. LOL Also a problem area could activate other DTC that have no real problem themselves. So getting a DTC and understanding them, and clearing and rechecking them and the monitors is the first step to diagnosing an issue that a DTC was activated.



ASE

 

It looks like there was another person that responded to you in I would have gone with my gut. The mechanic told you it was the cord. I have had someone mess with my car so I would think he was a hero for fixing it. I'm not a mechanic by any means, but I can read people. And yes, if my doctor went fishing for things wrong with me and then decided it was my leg and cut.off the wrong one, I would definitely not pay for it. Also this website is not even that easy to use....If you don't want anyone's opinion, don't ask for it, or say you only want other mechanic's opinion.

 

Hmm new member and your second contribution to the forum. auh ok then!

It is not called fishing but electrical diagnostic trouble shooting more or less a better phrase then fishing which fishing implies maybe you will catch something and maybe your won't. Quality and reputable service shops (look for the ASE signs on the building and certification of those ASE trained and certified Automotive Technician generally hung in the office in plain site for customers to see) will give you a written estimate you agree to. Most electrical problems like a battery voltage depletion problem, the charging system and battery health (as long as the battery is fully charged) or the circuit (fuse or relay controlled ) voltage drain can found in an hour. Not resolved but found! After which an additional service charge estimate to repair it may need an authorization from the owner depending on the states business regulations for operation. In my shop all service work or diagnostic trouble shooting is detailed in writing on the work order and signed and or approved or initialed by the customer even if the customers chooses not to have the work performed.

Plainly reading carefully the first post IMHO (in my humble opinion) the shop does not have the experience to properly be doing electrical diagnostic trouble shooting!