So I've been hunting this battery drain down for about a year or more now. It went away with the warm weather but I've been reminded that my problems just don't go away. It drains my battery while I'm at work on a typical 8hr day after 25 minutes of highway driving. I have to use a battery jumper atleast twice daily. With an amp clamped on the battery pos cable, it was drawing .2-.5 amps. I narrowed it down to the No.9 10a fuse in the box underneath the hood. When fuse is pulled, the draw drops to 0.
No. 9 fuse: "Audio Unit, Back-Up Light, Data Link Connector (DLC), Gauge Assembly, Immobilizer Control Unit, Keylees Receiver Unit, Multiplex Control Unit"


Starting with the stereo, I unplugged and removed it dropping the draw down to .043 on the pos bat. cable. At this point i was flooded with mixed emotions. Happy that I finally gained some ground but distraught now that I had to research how to get to/test these other components. After spending all night in the cold after work testing these components one after the other, I finally made more headway. The ****ing Multiplex unit. Something I know very little about(not for lack of trying) and can't seem to find much information at all on it. Apparently the MCU is assembled together with the fusebox behind the steering column.

I've been through hundreds of pictures, diagrams and plenty of service manuals attempting to find some sort of details on the MCU attached to the fuse box. All the diagrams show info for the fuses, but where the MCU has plug connections they are always blank in the diagram. I've spent several nights sifting through forums,manuals and videos. Where I'm working I currently have to park in a paid/gated garage, I'm terrified of my car not starting and it getting towed or myself hit with a massive parking fee.

Moving on...I put the clamp on every single harness I could reach that was plugged into the MCU. After smashing my head against the brake pedal with my feet sticking up over the headrest for about 2 hours. I found a connection that had a draw.


Unlike the battery which reads a consistent .04 amps, the clamp on the wires above are very sporadic, jumping from .01 to .05 amps, but seems more often to hit the .04 mark. This is where I'm lost and need some guidance or direction.



Maybe relevant info:
Alternator replaced twice(not because of drain.)
Battery replaced and tested. Unplugged overnight its fine and can start the car right up when I put it back on. This is hell on the terminals though.
Starter replaced(this is what I thought was the original villain when I started this journey, it needed replacement, but had no effect on drain.)

Throw me a bone here guys, I'm desperate. Me and the wife both absolutely love this car and I can't afford to have my only vehicle go down while she's in school.

 

I will preface this response with the usual disclaimer that I have no model specific experience. New models have
a similar situation caused by things like the drivers door handle sensor or modules that are not going into sleep mode after shutdown. Finding those is difficult at a minimum.

What I can offer is experience dealing with vampires or other concerns on vehicles that I have eliminated the drain issue on immediately and inexpensively. All I did was to install a battery cut off switch.

The first one is on my dual “house” batteries. It is a simple top mounted switch that you unscrew to disconnect. You would need a top post mounted version for your application.

The green **** screws into the shunt to make connection.

My second solution is a hardwired key switch under the dash in my Smart. It is required to flat tow.


1/4 Turn to remove. Push + 1/4 turn to connect. The - cables attach to the back of the switch.


I know this does not solve your issue but it can make your V dependable again.

 

I might give this a try if I can't find the culprit very soon. I REALLY appreciate the extra detail and pictures describing how you did yours, thank you!

 

Sorry, I did not read your post very carefully. It was … a bit long … and my attention span wavered.

the MCU is part of the fuse box, it can’t be separated unless you take the fuse box out and pry it apart. It acts as a rudimentary body control module.

as for the fuse box connector, each of the connectors has a letter associated with it. I believe it’s printed on the fuse box with a circle around the letter. Once you find the connector letter, you can cross reference with this page:

https://charm.li/Honda%20Truck/2004/...ector%20Views/

as for the battery draw, seems like the majority of it was in your audio unit. With it unplugged you’re down to 40mA? You should have much better battery life already. Have you looked at the accuracy specs of your clamp meter? My Klein clamp meter accuracy is 10mA, so when I’m down in the range you’re at, I have switched over to a traditional DVOM meter where you connect your leads into the circuit.