TL;DR My 10A backup fuse blows when I plug in my wifi-enabled OBD scanner. Replaced fuse and stopped plugging the scanner in, but now other dash lights come on intermittently. What should I do now?

A couple of weeks ago, my son was driving home with a few of his friends in our 2016 Accord, and they stopped to help someone who had gone off the road. When they came back to the car after 15 minutes or so it was completely dead and would not start. Someone else that had also stopped tried to jump it, to no avail. So I ended up picking them up, and had it towed back to the house the next day since it was very late and AAA basically told me I was out of luck until the AM (that's another story).

Once it was home, I tried jumping it myself just to see, but no luck. Tested the battery, and it seemed good. Cleaned and reseated all the connections. Still nothing. Then I checked the fuses starting with the main battery fuse which was good. Turns out the 10A backup fuse (#15) was blown. After replacing it, everything suddenly worked. Not sure why it had blown, but it had no issues for almost a week.

Then, a couple of days ago, my son took the car to school, and when he went to come home, it was completely dead again. So I went up to help, and we checked the backup fuse and it was blown again. I didn't have a spare so I borrowed the 10A audio fuse just to get him on his way. He headed off with his friends to grab some food. When they came out of McD's, it was dead again. He called me and I had him replace the fuse by himself using the 10A horn fuse and told him not to shut off the car until he got home.

When he got home I went to look at it, and I happened to notice that the OBD port was dislodged from its bracket, with the OBD scanner we have still connected to it. Then I remembered that the night it first died it had been dangling down and I had reseated it back up underneath. I asked my son if he kicks it loose by accident often and he told me every once in a while he does. So I immediately decided to run a test.

I disconnected the OBD scanner, and replaced the blown fuse (and the ones we cannibalized) and it immediately had power and started. I turned it on and off 4 or 5 times with no problems. Then I plugged in the scanner and it started once. Then when I turned it off, it was dead like before. Blown fuse. So mystery solved. The scanner was causing a short. Thought that was the end of it.

But now the power steering and VSA lights are coming on every few runs, but go away after turning the car off. And every so often the Brake dash light will come on for a minute or so then go off. I can't check the codes since my scanner won't work. I am thinking I will grab a new scanner and see if it still blows the fuse or not, but clearly something else is going on with the electrical.

Anyone have any ideas on how I should proceed before I bring it to the shop along with my wallet?

 

To get some direction, you can stop by a parts store and have them scan for codes.

I don't have a 2016 shop manual or wiring harness, but the backup fuse on a 2010 accord protects the power feed to the OBD2 connector. The fuse also protects the gauge control module, the driver & passenger MICU (multiplex control unit), hands free control unit, the immobilizer, the power window master switch. I suspect the 2016 accord is similar on what that fuse protects.

I'd inspect the connector for the scanner and the wireharness near the obd2 scanner for any obvious damage. You may want to remove any electrical tape and peel back the plastic loom to see if any damage is done to the wires in that harness. I'd work back to slightly past the point where the harness can't move, like where the harness ties into a another harness or an anchor point for the harness.

 

I got to examine the OBD2 connector and the white wire has a tiny spot where the insulation has come off, but nothing else I could visually see.

When I went to reseat the connector in the metal housing, it visibly sparked and blew the fuse. It seemed to spark when a corner of the plastic connector touched the metal housing, but it was hard to tell the exact origin of the spark. I am guessing a pin touched metal or there was part of some other wire exposed that touched and shorted.

I'd like to replace the whole thing, but I couldn't see exactly where the whole thing connects back to. Every light is currently on and stuck that way.