dbasil

Bought this 05 bmw 545i not knowing it had a battery drain went to the mechanic changed the alternator and the battery and still having the same issue, the diagnostic showed that none of my kcan modules could communicate with each other but everything in the car pretty much works. Im thinking it could be the kbm itself. If i get a new one would it be plug and play or will i have to code it to the vehicle?

seanjordan20

Don't guess make sure you find the module draining before replacing anything. I would check fuses to see which module is draining the battery

dbasil

which fuse box should i check? The one in the glove compartment or the one in the trunk above the battery?

seanjordan20

What I do is leave the trunk and passenger door open. Once the car goes to sleep (or after 15 mins) I start the parasitic draw test. Takes about 5 mins per fuse box. Once you find the module still drawing power then you troubleshoot to conclude if its the a part or the module causing the issue. Of course I do a visual check first of the known problem modules just in case I can see something visual.

habbyguy

There are a couple easy ways to do parasitic drain testing.

You can hook up an ammeter. The old school variety requires disconnecting the battery and inserting the leads between the battery and car, and is prone to blow the (usually 10 amp) fuse in the ammeter when something in the car wakes up (especially a BMW). My favorite way to do this instead is to use a meter with a clamp-on DC ammeter function (careful - most clamp-on multimeters only do AC amps with the clamp). Even better, I found one that does a remote access thing through a Bluetooth app, so I can clamp the meter around the positive battery cable, and close up the car (so there are no dome lights on). The one I got wasn't at all spendy, and really saved me some time. Here's the one I got (not saying it's still the best deal out there - but it shows how much functionality you can get for chump change).

The other way to do it is to measure the (very small) voltage drop across all the fuses. Because the voltage drop will be proportional to the amount of current flowing through the fuse, this is a quick and easy way to test each circuit for current drain. Here's a quick chart / description that may help.