Several months ago I bought a 2006 1500 Suburban Z71 w/130k miles. After a month or so I started getting the left door ajar message and the dome lights staying on. I overrode the lights and put dealing with it on the backburner. Last month I started having problems with the security system activating frequently which I figured was an issue with the car thinking the left rear door was ajar with the security armed. I disabled the security as a temporary fix and then the situation devolved further into the car dying after sitting for 12 or so hours.

After hooking up jumper cables and getting a sufficient charge I could get the vehicle to start but then it would immediately die. This would happen over and over. If I disconnected the jumper cables and cranked it down to nearly dead and then reattached the cables again then I could start it up no problem. I was able to replicate this procedure. Any ideas as to what this was? Security disabling the fuel delivery?

I searched for parasitic draw today and found approx. 3 amps of parasitic draw. Three of the main contributor fuses were INFO (onstar and rear entertainment research shows), RADIO (aftermarket radio installed) and IPC/DIC. However, when I pulled just the BCM fuse it dropped to .04amps. This was further evidence that the BCM is haywire after the door ajar issue.

This leads to my main questions of:

Can the BCM conking out result in parasitic draw?
Do I have to have a pre-flashed BCM if I buy one online and also do the key on/key off 10 minute programming routine?
Is there any way to force a reprogram of my already installed BCM to see if that might fix it? Someone said online that it was possible, but I can't get the security light to stay on for 10 minutes as the procedure dictates.

 

1) Yes the BCM can create a draw if it’s malfunctioning, but more often than not, it just doesn’t shut down and go to sleep when it should be. Reasons for that can vary from things like detecting a door is open when it’s not, communication problems or communication from another module, a shorted power or ground circuit... the list goes on.

2) Some vendors can program by VIN but the pass lock will still need to be learned. The reason the security light doesn’t stay on is because it’s already learned the resistance of the key you have now and doesn’t need to be learned.

3) You can reset the BCM (and all the modules) by disconnecting both battery cables and clamping or jumping them together for at least an hour - this discharges the backup batteries, clears all adaptive memory, and can eliminate internal glitches. In your case I’d recommend doing this overnight to be absolutely sure.

That said, you need to restore the security system to its original condition before hooking up the battery again. Then you can start troubleshooting whether or not the draw is still present.

 

Thank you for the reply. Can you please elaborate more on restoring the security system to its original condition? How can that be done before reconnecting the battery so it has power?

 

In your first post you stated you disabled the security but didn’t explain how - I only meant you should reverse whatever you did to disable it.

I also forgot to mention that something as simple as weak battery connections can cause several problems as well. Make sure all battery cable connections are clean and tight on both ends. You should also charge the battery while it’s disconnected and clean the battery terminals. Even if they’re not covered in corrosion, clean, shiny surfaces on the battery and terminals is the best way to ensure adequate contact.

Since I don’t know what procedure you found, here’s how to relearn the pass lock system (in case the disconnect clears it - I don’t remember if it will or not).

1) Turn the key to on/run and check the cluster to make sure the pass lock indicator is on/functional during the bulb check (all indicators turn on for a few seconds).

2) Make sure all accessories (HVAC, radio, etc) are turned off and unplug any car chargers or equivalent devices to prevent any other draws on the battery. If you’re concerned the draw is still present (such as seeing the door ajar message), hook up a charger.

3) Attempt to crank the engine, then release the key to the on/run position - the pass lock indicator should turn on and remain solid for about 10 minutes, then go out.

4) Turn the ignition off for at least 5 seconds.

5) Turn the key to on for a second or two (the point is to give the PCM/BCM a chance to establish communication) then attempt to crank and release the key to the on/run position until the indicator goes out again. Repeat one more time.

6) After the 3rd cycle, key off for at least 5 seconds before attempting to crank - the 4th crank attempt is when the pass lock sensor will be learned.

If this is successful and the suburban is driveable, go on a 10-15 minute drive. When you return, set up for the draw test and make sure to cycle every function/accessory you can think of. Then give it at least 45 minutes for the modules to power down - if the draw is still above 25 milliamps, give it another hour. If it’s still above 25 milliamps, proceed with circuit isolation testing.

 

Oh I see. I meant that I disabled it in the steering wheel button/command center screen. My concern is draining everything out and then getting stuck being unable to start the car. Which I'm not sure if that is how the security works.

Conveniently Chevy decided to discontinue the 03-07 Suburban BCM last month and they are in short supply nationwide. I called dealers all over the US and they said they've been getting inundated with calls looking for it. Way to go, Chevy.

 

In that case, leaving it disabled shouldn’t hurt anything. I thought perhaps you’d cut or jumped some wires to disable it.

If the BCM turns out to be faulty, there are repair services available. You’ll have to send them the module so you won’t be able to drive it, but they’re much cheaper than a replacement.

 

Thanks. So just to be sure, if I drain it with the wires connected and reconnect to the battery, the only process I have to complete is the key lock process you already shared? I wouldn't have to take it to a shop for any other flashing/reprogramming?

 

You might not even need to relearn the pass lock - I’m not sure so you’ll have to see what happens once the battery is connected.

This procedure (known as a “hard reset”) clears all learned and adaptive memory from the modules. It basically resets them to their condition immediately after production. It won’t clear essential information like the VIN and basic programming that allows the vehicle to operate, but if there’s an internal glitch not related to circuitry, a hard reset could resolve it. It’s no guarantee, but certainly worth a shot before replacing a module unnecessarily.

For example - if the door ajar message is the result of a glitch in the BCM (as opposed to a shorted circuit), a hard reset might resolve it. But if the message is still there after the reset, you’ll want to confirm the circuits for the door switch aren’t shorted together or the door switch itself isn’t stuck closed before condemning the BCM.

 

Thanks Gumby. You've been very helpful. I will give the hard reset a go first.

 

Just an update for future readers (because I hate when these threads just die off with no resolution):

Reset did not work. I sourced another BCM from an '05 at a junk yard and have that ready while I continue to investigate the door latch assembly. From what I understand, the 4 pin plug that connects into the latch has pin B as the one that sends a signal to the BCM confirming that the door is closed. Simply unplugging the power to the door latch assembly will not solve the door ajar issue. I will be testing it by grounding out pin B. The gear-driven switch in the actuator of the latch assembly appeared to be mechanically functioning well.

Update 3/29/21:

I was misled by some of the wiring discussions and it turns out that the door latch does not have to send a constant signal to the BCM to indicate door shut. Thus, simply unplugging the top plug inside the left rear door fixed my issue immediately. No more door ajar, no more power drain. Leaving the second wire plugged in enabled me to keep power locks as well.