Replacing BCM

[gemr]

Our auto elect is stumped. Cannot find cause of battery draining and thinks it might be BCM.
Already spent heaps with timing chain disaster (2007 D40)so was looking to buy $200 second hand BCM to see if this fixed the problem.

Is it simply a matter of unplugging current one and replacing with new one?

Another thought was to install cut off switch to battery ?

Amy ideas appreciated.

 

[Old.Tony]

BCM controls the entry to the vehicle so it's the component responsible for your key remote.

The BCM is just a small computer that controls other devices. It's unusual for it to be consuming large amounts of power, it would be quite warm if it were using a lot of power, that's what I'd check first. If it's cool, I'd look elsewhere.

The D40 has enough "automated" stuff on it to drain a reasonable battery inside about 5-7 days. If the battery has a bit of sulphation in it, the battery will drain itself. Combine the two (sulphated battery connected to a D40) and it might not last 2 days. If the battery is old and only accepting a surface charge, it might last less than that.

The very first thing I'd do is measure the current drain from the battery. The auto electrician should have a clamp meter and be able to test current draw (with ignition off) through the battery negative lead. If it's <1A then I'd suspect faulty battery.

With ignition off, most systems are off except for the BCM, door locks (via the centre switch), NATS and (if installed) the CouplerTec anti-rust device. You could safely remove that and file it in the green cabinet that gets emptied on Wednesday mornings.