BCM won't go to sleep mode

[michalg]

Hi,
I have the problem with battery drain in my 2000' Astro AWD. The symptoms are as following:
there are ~300mA drain during first 20 minutes after everything is switched off and closed in the van. Then drain drops to several mA when BCM enters sleep mode. But then, just after a second or two, drain raises again to 300mA. Then next 20minutes and so on...
Removing BCM fuse causes the drain to disappear, of course.
There is something that does not allow BCM to keep in sleep mode but I am not able to figure out what could do that.
I do not have any additional, non-factory equipment installed, as far as I know.
Any ideas/suggestions ?
MichalG
ps I am in Europe/Poland so I do not have GM garage nearby with some fancy computer code reader...

[MountainManJoe]

Dzien dobry.

The BCM might be receiving a false door switch signal. Also, check that ground connections are good.

[michalg]

Dzien dobry, timelessbeing !
Aren't those door switches the same as these responsible for switching on interior lights ? If so, then switches are working fine.
I could not think about something more clever than get into the three BCM connectors and try each of several wires separately. This gives me something like 20minutes for each .... the whole weekend in the car!
MichalG

[MountainManJoe]

Czesc

I'm still thinking about your problem, but maybe my reference material will help you:
https://docs.google.com/leaf?id=0BwFVqp ... FjMjAzZjY4

I recommend starting with "Body Control System Circuit Description" and "body computer.pdf"

All of these signals will "wake up" the BCM. Likely, one of them is malfunctioning.

• Door ajar switches
• Door handle switches
• Dome lamp
• Park lamps
• Power door lock switches
• Interior lamp request active
• Ignition key put into the ignition switch
• Ignition key removed from the ignition switch
• Ignition in the run position
• Key in door lock switch
• Liftgate release switch
• Liftgate jamb switch
• Remote control door lock transmitter request to the BCM

[michalg]

Thank you very much for sharing your materials - very, very helpfull.
I found out that something on the C2 connector to the BCM is making truble. Then brute force elimination method - one wire - 20min - another one - next 20min and the winner is ... B12 orange wire described as "INADVERTENT FEED" ("INTERIOR LIGHTS SYSTEM").
After removing B12 wire from C2 connector BCM enters sleep mode and stays in it. Drain is now ~80mA - still too much, I think, but much better.
I have no idea what is connected to the "INADVERTENT FEED" so far. I have to investigate it with more schematics in hands. I would guess that it could be alarm system or remote start system as this vehicle was such equipped probably by dealer. Neither alarm nor remote start is working at the moment.
MichalG

[MountainManJoe]

The BCM turns off inadvertent power relay after 20 minutes (1216 seconds) to preserve battery power. The 20 minute timer starts after any one of the following:
· Ignition switch is turned from run or start to unlock, lock or ACC.
· Illuminated entry is activated
· Interior lamps switch is turned on
· The liftgate is opened or closed
· Underhood lamp is activated
· Vanity lamp is activated
· Courtesy lamp is activated
· Dome lamp is activated
· Glove box lamp is activated
· Reading lamp is activated
· Inside rearview mirror lamp is activated.
If any one of the below inputs occur during the 20 minute timer period, the timer is reset to 20 minutes (1216 seconds).
· Ignition switch is turned from run or start to unlock, lock or ACC.
· Illuminated entry is activated
· Interior lamps switch is turned on
· The liftgate is opened or closed
· Courtesy lamp is activated
· Dome lamp is activated

Check the "Interior Lights Courtesy Lamps 1of2.pdf" file.
It shows the 'inadvertent power relay" circuit diagram
C2B12 leads to splice S258.

Then you can check these documents: https://docs.google.com/leaf?id=0BwFVqp ... 0&hl=en_US
and open "2003 Electrical Component Locater.pdf"
S258: In instrument panel harness. 13cm from radio connectors breakout.

[michalg]

I had been pretty sure that the problem was in the "overhead console", because wake up signal disappeared after I removed and disconnect it.
Unfortunately, when I connected it again the problem has gone. So now, BCM goes to sleep fine, but I am not sure which of ~hundred things I touched did the trick. So I am afraid **** will come again.
Anyway, many thanks for the tips and diagrams. I would be lost without them.
MichalG

[MountainManJoe]

Sometimes just taking things apart and putting them back together will fix a problem.
Glad I could be of help.

[tickerguy]

I know this is old but.....

If you run into this on a GM van check not just the pin switch on the door (if the lights come on when you open it that's working) but ALSO the two-pin "spring-loaded" connector that goes to the locking mechanism. THE BCM MONITORS THIS AND IF IT THINKS ITS OPEN IT WILL NOT GO TO SLEEP!

Corrosion on the two pads will cause this connection to be intermittent and then.... no sleep and a nasty battery drain.