I hope I am in the right place, as this is my first post. Sorry if I screwed it up.

At this point, this is more of a post to inform everyone of what issues I had, how I troubleshot them, and hopefully the fix, in case anyone else is having the same symptoms I can save them the multiple hours of research. However, any insight will be very appreciated. I am self-taught on everything I did from this Forum as well as other places of similar nature on the internet.

I have a 2018 Ram 2500 Laramie, tuned, with an MM3.

Any other electronics I have on my truck are through a separate fuse panel and I have that disconnected to rule any of them out.

Last week I came out to a dead truck that was sitting for 45 hours. (4 volts each checking with a voltmeter directly on the batteries)

So the troubleshooting began.

I charged up the truck with a tender overnight and started with testing the batteries and alternator.

All checked out. (740cca batteries and they showed about 750cca.

The alternator charges fine and the diodes are working properly)

The next step was the parasitic draw test.

Disconnected the negative on the driver side, run a jumper, disconnect the passenger side to the negative.

Hooked up amp meter probes on the driver's side and remove the jumper.

It was all over the place ranging from 1.30 to 4.80 amps (Yes Amps not milliamps).

I started pulling fuses one by one until I finally got to the diagnostics fuse.

The problem went away and the draw dropped significantly down to 80 milliamps for a few minutes and then down to about 30-50 milliamps after it went to sleep mode.

I confirmed this 1 more time and the same thing happened.

With the fuse replaced, I disconnected the MM3 from the OBD2 port and checked again for amp draw.

This woke the truck up so I had to wait 10-15 minutes before it went to sleep again, but this fixed the problem (But only while it is unplugged from the OBD2 port).

I also used an ammeter clamp after putting the batteries back together and it was still showing 30-50 milliamps after the truck went to sleep mode. (Sorry I am a little redundant)

I contacted Ray and got back to me immediately!

He pointed me in the right direction and told me to contact MM3power and provided an email to their support team. (Thank you, Ray)

I spoke to Dirk from MM3 and told them what I had done and he was extremely helpful.

He asked me to run a couple of other tests for him to confirm his suspicions.

He believes it is a bad cable from the tuner's black box (Sorry I don't know the name of the part) to the OBD2 port so he told me he would send me a new cable to see if that solves the issue.

I hope that this does solve the issue and I believe MM3 will figure it out, but I don't understand how the cable could go bad since I have not unplugged it or messed with it since the install a year ago. (I'm still hopeful though as Dirk seemed very knowledgeable)

My issue now is I am paranoid about coming out to a dead truck again, so after a 30+ minute drive and a few minutes after the engine is off I will check the battery voltage. At that point they show about 12.7 Volts, however, 7 hours later they are already down to about 12.35 Volts.

I'm thinking I ruined my batteries when they drained down to 4 Volts so now they don't hold a charge as well but I don't want to buy new batteries until I know everything is fixed.

Does anyone know what the normal draw on these trucks should be? 30-50 Milliamps seems like it should be about right.

I am going to be out of town starting tomorrow for a coup of weeks hunting in the sticks with no service, so I apologize in advance that I will not be able to respond or check this thread. I will check it when I get back as well as give an update on what happened.

I hope I provided enough information to make this make sense!

Any questions I will get back to you as soon as I can.

Thanks,