Significant battery draw on my 2007 Honda Odyssey until I remove the fuse labeled "Back Up, ACC". 40A square type fuse. what circuit does this fuse protect?

I would read 'Back Up' as reversing lights and camera if equipped.

Fuse Box Diagram Honda Odyssey (RL3/RL4; 2005-2010)

https://fuse-box.info > honda > honda-odyssey-rl3-rl4-...

The interior fuse boxes are located under the dashboard on the driver's and passenger's side. The location of the fuses in the passenger compartment: Honda ...

Honda Odyssey (2006 - 2007) - fuse box diagram

https://www.autogenius.info > honda-odyssey-2006-20...

May 14, 2017 - Primary engine compartment fuse box ; 1, 10, Left Headlight Low ; 2, 30, Rear Defroster Coil ; 3, 10, Left Headlight High ; 4, 15, Small Lights.

https://www.google.com/search?q=2006+honda+odyssey+fuse+15

..

There could be a fuse or relay issue since multiple systems became inoperative simultaneously. I'd suspect that when the alarm went off, someone targeted and disabled the horn system so that it wasn't honking inside the repair facility. Both the horn switch and cruise control switch are located in the steering wheel and therefore they share common components and circuitry. Try checking under-hood fuses #7 (7.5A), #13 (20A), #15 (40A) and #20 (40A), as well as under-dash fuses #7 (7.5A) and 21 (7.5A). If all these fuses are OK, much deeper diagnosis will need to be performed. One somewhat common failure item is the spiral cable (also called a clock spring) that transfers power to the steering wheel (while allowing it to turn). That part can be seen within the steering angle replacement procedure shown here: https://www.yourmechanic.com/article/how-to-replace-a-steering-angle-sensor-by-marvin-sunderland

Voltage is not the means to find the drain, even a minor switching circuit may show 12 volts. The only thing g to test that way would be to disconnect items in the circuit ( a listing can usually be found in the owners manual or other tech publication ) until the reading drops. Check amperage across the fuse, make sure meter has a good fuse, not foil over a blown fuse. If amps is less than .02 A then the drain is acceptable.

On this website, you find fuse box diagram and description for Honda Odyssey (2004)

Honda Odyssey 2003 2004 fuse box diagram Auto Genius

You need to disconnect the battery negative lead and place an ammeter between battery and lead, note the current draw with every thing switched off, then start removing one fuse at a time from fuse box and see if ammeter drops significantly if not refit fuse and remove the next one and repeat this until you find the one that causes a significant drop, then you will have found the circuit that is draining the battery, you need to check this circuit to find cause of power draw and repair as required, let me know how you get on

If there is an amp draw whilst everything is turned of an easy way to isolate the problem is by using an amp metre. In the main fuse socket take the amp reading. Now one by one remove each fuse until the amp draw disappears. Be sure to place each fuse back in its place before removing another to ensure you have them in the correct position. Once you have removed the fuse that eliminates the current draw you must look at the fuse box cover and see witch circuit you draw is in.

ok , i dont believe fuse 13 draws 40amps, sorry.

did you use an ammeter, and if not an ampclamp meter this is harder.
here is a page that shows all ways to find phantom drains.

http://www.fixkick.com/drain/drain.html


12x40 is near 500 watts, no way, if you had drain link that
there would be
1: huge light.
2: huge heat
3: or huge noise.
for sure. 500watts dont just fly way like a bird, not in this world.
no lie we can find, it, but first tell what tools you have.
really.

Yourself?

(Has been discovered)---failed to resolve your
problem

Why do all the shops not repair anything? You
stop them or take the car back too soon?

Why wasn't the acc module checked for timing out?
They found a current load or a just a voltage drop on
#15 fuse !!!

What you do is pull off the pos cable. Touch it to the ground cable for a couple of seconds to discharge any voltage that may be lingering in the cars circuits. (Leave ground wire hooked to battery. Only the Positve should be unhooked) Now hook your meter between the Pos Cable and the Pos of the battery. It should show anywhere from between 0-2 volts. maybe more if you have a alarm system. If it shows anymore then 3-4 volts you have a parasitic draw. Best way to Isolate this is to start pulling fuses one by one until the meter jumps down to zero. Then plug other fuses back in. If meter dos not go back up. you have isolated the circuit that is draining the battery