Replacing a BCM with a used one

I've been having trouble with my power locks; they unlock reliably but very rarely do they lock. It's been doing this for the last 2 years and I am so fed up with it I finally tore into my dash and did some poking around. I think I've traced it back to the BCM. I replaced the ignition switch a couple weeks ago and it did NOTHING. All that's left in the chain is the BCM... right?

I found an exact replacement for mine on ebay. Question is, can I just swap them and go? Or does it have to be reprogrammed and all that jazz?

Thanks!

It sounds like you've been poking around quite a bit, and have an interesting question. Without Alldata for the Intrigue handy I went to the free demo site for alldatapro. It looks like the 2003 Bonnie has a door module in each door that communicates with the BCM. I'm not sure how close door operation would be between the two GM platforms.

I would think you could just swap them, but I'd wonder what the calibration ID inside the BCM is. If you had your VIN, and the salvage VIN you could run them at http://tis2web.service.gm.com/tis2web which is free..

I'm not sure if this calibration ID # is for all modules or possibly just the PCM, which your not working with. But at least you'd have some kind of clue that the module that your getting is out of the same vintage Intrigue.

I do know that that VIN is passed on the car's serial network. However I don't know if the BCM stores the VIN and has to see it to be operational. In the 2002 Intrigue's the Radio is set up that way. If the VIN of the radio doesn't match the network, then the radio won't power up it's dead.

I guess it all depends on the cost of the module your looking at as to if it's worthwhile to try. You think you'd have more than just lock issues with a bad BCM. Maybe you do, I didn't read your ignition switch issues..

Good luck and keep us posted

Thank you for the info! This BCM is $50, not the end of the world I guess, if it didn't work or didn't fix anything. No other electrical problems, I replaced the ignition switch specifically for the lock problem.

I messed around with it more and found if you turn the key to ON, shift the transaxle in and out of park, then pull the key out and press the lock button you can hear the relay in the BCM click once, but it doesn't send enough power to actually lock the doors. Also, if you let the interior lights fade out when the key is pulled out, the relay will click once, but again the doors don't lock.

I also found if I pulled the harness which goes to the door lock switches out of the BCM almost all the way, it would lock for 8-10 cycles then die out. Turn the key off and on again, lock for 8-10 cycles, die out. I can't even get it to do this anymore though. The connection was clean, wires are in good condition. Maybe I was bypassing something by doing that.

I don't know what any of that means, however. I'm still leaning towards BCM. This car drives me nuts sometimes...

It sounds to me like you have an issue with the lock power on the other side of the relay. If the relay for the doors is clicking, you would think the BCM is sending out a sufficient signal.

Does the signal from the BCM go through a switching relay to the door actuator, or does it go directly from the BCM to the door? I can't imagine that the door lock actuator takes that much current, but then the BCM isn't designed to provide high current outputs.

Do you have a wiring diagram for the BCM? I might have one on a different computer that I'd have access to in a few days.. Send me a PM with an email address and I'll look.

How about bringing power and ground right to the door lock switch contacts? This jumper would make the doors look consistantly.. At least give you the confirmation that it's not an issue with the door or switches.. I'd suspect the drivers door switch, as the power for all the doors goes through that. At least that's the way it was on a mid 90's Oldsmobile when I was working on lock/window issues..

All through the drivers door switch huh? Looks like they aren't wired like that anymore. Each switch seems to send a low current signal to the BCM, and the BCM then sends high current directly to the actuators.

I just looked at that link you sent me. Very interesting, thank you. I pulled the BCM apart yesterday, but I didn't look very close at it. I thought about replacing the lock relay on it, but I have a hunch it's not the problem. Thanks to that link, I think I'm gonna pull it apart again and look for any fried controllers this time...

I didn't look that closely on the pictures in the link, but I didn't specifically see the "fried circuit" that the author was talking about.

If you find it snap a picture and post it.

Good Luck--

So I took the BCM back apart, everything looked great. Then I started playing with the locks some more and they all became very weak even though my battery was fine. However, the lock relay in the BCM started clicking fairly reliably.

So I started to suspect a seized actuator. No idea which one it could be, so I manually locked and unlocked all my doors to find the one which gave me the most physical resistance, and the passenger rear door did just that. So I pulled the panel off (what a b!tch that was!) pulled the latch mechanism out and took that actuator out of the circuit. Sure enough, the locks instantly worked perfectly. The actuator was drawing too much current.

This is a very bittersweet moment for me because a seized actuator is what I suspected in the first place, but I didn't want to go pulling random door panels off to check. What kills me even more is I bought that ebay BCM this morning! Hopefully I can re-sell the stupid thing.

Let that be a lesson to you kiddies, don't cut corners hoping you'll get lucky. And don't go buying parts until you're SURE it's what you need. $100 in parts and several hours of my time and labor to find out I needed a freaking $10 actuator. Grrr...

Well I'm glad you figured it out, but yea it sucks when it turns out to be something easy.

Contact the seller, and try returning it offering to pay a restocking fee.. That would be free money for the seller, and would save you the hastle of selling parts. I've got two engine sets of plugs with wires.. Brand new GM part numbered stuff, that I've yet to install, and one of the Intrigues is limping.. So I'm also collecting a fair share of parts..

Well glad it's done.. I'd still be interested to know if you can swap modules and keep it running if you into a science experiment..

Got my new door lock actuator yesterday, installed it today and the problem came back!! Ahh! However, UPS just showed up with the BCM I ordered, so I threw it in, crossed my fingers and turned the key... The locks work! It won't start, obviously because the new BCM doesn't like my Passlock module. So I'm doing the 20 minute relearn procedure right now and hoping for the best.

By the way, my jaw dropped when my keyless entry remotes still worked. Is that system not a part of the BCM or did I just get insanely lucky? I thought for sure I'd have to go to the dealer and get them to match my remotes up to the new BCM.

After two hours and several tries, the Passlock relearn procedure finally took. Engine fired up and everything works great! And holy crap, door locks are powerful now. I didn't realize how weak they were before.

This could not have gone smoother, I should go out and buy a lottery ticket!

Glad I bought that BCM after all...

So it sounds like you ended up needing the BCM after all.. Good find with the sticky lock actuator, or you might have been doing this yet again after frying your new BCM.

The keyless entry remotes send a signal to the keyless entry transmitter reciever. I think it's under the center of the dash assembly. The keyless remotes must talk to this module, with this talking to the BCM.. I vaguely remember seeing this when I was looking at the schematics for the dash.