SnowMan01

I realize these forums are not for my type of vehicle but I have read some very interesting, detailed and knowledgeable discussions regarding BCM faults. Can anyone here give me some good advice regarding a problem with my vehicle which I think is BCM based?

RevGTO

iTrader: (12)

I don't think anybody can answer that until you describe what the problem is.

SnowMan01

I didn't want to make a long post describing the symptoms and
what I've done so far because I was not sure if, because my vehicle is not the subject of your discussions here, that anyone would respond. I've found other discussion sites but they don't appear to have knowledgeable people that can get into the kind of detail I've seen here.

SnowMan01

I didn't want to make a long post describing the symptoms and
what I've done so far because I was not sure if, because my vehicle is not the subject of your discussions here, that anyone would respond. I've found other discussion sites but they don't appear to have knowledgeable people that can get into the kind of detail I've seen here.

G Atsma

Well you're here now, so lay it out....

SnowMan01

OK here goes. Van had no signs of any problems until one day both fobs (mine and the wife's) would not open the locks. So manually opened the door with the key. When I inserted the key into the ignition nothing happened, usually I get a "key in ignition" message on the dic. When I turned the key to the first stop nothing changed (no radio which usually comes on). Turned the key to next stop (accessory position?) the mil lit up but NOTHING else, no seat belt icon or ANY icon lights. It wasn't looking good. Sure enough when I tried to start the van by turning the key to start position absolutely NOTHING happened. Dead as a door nail! My worst of fears. I knew nothing of bcms, ecms, pcms or any control module. I have worked on all my vehicles in my driveway for almost 50 years but these terms were all new to me.

To make a long story short I did lots of internet research to educate myself and decided my bcm may be to blame. I went to the local wreckers and pulled one off another 2009 van (only cost me $20 so I thought it would be worth a try) just like mine with same part number. Installed it my van and everything seemed OK. Got the "key in ignition" message on the dic, radio came on and door lock fob worked. ALL the normal icons came on when I turned the key further so I figured I was off to the races. However when I tried to start the van nothing happpened. After releasing the key from the start position the radio went off and a "locked" message appeared on the radio. Also the dic displayed a "starting disabled" message. It appeared to me that the original bcm was faulty and what had to be done was a reprogramming of the wrecker bcm to be compatible to my van. I called the dealer and was told the problem was probably NOT my bcm and that the replacement bcm probably just reset something else in the system and that is why it reacted differently. They wanted me to take (tow) my van in so they could troubleshoot the problem. This made NO sense to me so if what he said was true and that something was reset then I should now be able to reinstall the original bcm and all would be well.
So I tried my original bcm but again nothing happened so I put the wrecker's bcm back in and it performed as before, everything normal until I tried to start the van. I have been swapping the two bcms back and forth for a few days now with the same results with only one exception - the original bcm worked one time only and I was able to get the van started. But when I turned it off and waited a minute or so the original problem returned. All other attempts of removing and reinstalling the bcm failed. I must have done it an additional 6 times or so. It seems to me that this would indicate an intermittent problem with the original bcm.

I have done scans of all the control modules. The ecm had about 70 error codes, all of which except for one were P codes. There was one U code which stated the ecm lost communication with the bcm. The tcm had close to 30 error codes - all P codes. The original bcm could not be scanned - received a message saying no communication. All other modules passed with no error codes.

If the problem is the bcm, should an autoshop with the right tools be able to reprogram the replacement bcm from the wreckers? Shouldn't that solve the "starting disabled" and "locked" message on the radio? Does anyone think the problem is definitely the bcm from what I've
described?
Sorry for the long post, tried to keep it as short as possible and still make it clear as to what I am up against. Don't want to go to a dealer unless it is absolutely necessary - I've heard of a lot of horror stories.

G Atsma

One question, and maybe a dumb one. Is the battery charged??

SnowMan01

Battery is in excellent condition. Cleaned all battery posts and connectors. I always keep a maintenance charger on it. Headlights work great - nice and bright and the wrecker's bcm ALWAYS fires up well. Only problem is starter is disabled. Looks to me that this message is from the vehicle's VATS system because the wrecker's bcm is not programmed to the vehicle.

RevGTO

iTrader: (12)

Here are some hazy recollections from my experiences with f-bodies and our 99 Montana that may be of help.

1. I don't think you can swap BCM's between vehicles. They are keyed to the PCM and VIN of the original vehicle and just won't work on a different car. You have to obtain a new one and have it programmed to get it to work. I'm pretty sure this is true, especially in the case of 4th gen f-bodies. Hence the locking on the radio, etc. They can't communicate.

2.We had a vexing no-start condition on the 99 Montana late in its life. It would crank, fire, and die. We found out it was a problem with the ignition module not recognizing the transponder in the key, prompting fuel shut off - a VATS problem. I bought a bypass kit for it (still have it) but the problem was solved by a new key (programmed at the dealer). All this to suggest that perhaps the later model Montanas had different Passkey system that not only cut off the fuel pump, but disabled the starter as well (like the 4th gens). In that case, a new reprogrammed key or a bypass could solve the problem. Here's a link about programming the key

SnowMan01

Thanks for all your good info. I would like to get your opinion on what you said about the replacement bcm from the wreckers. Do you think it can be RE-programmed for my vehicle? I have read conflicting stories. Some say it is possible, others say it is impossible, the naysayers are usually dealers so that kind of tells me something. My scan of the ecm with the wreckers bcm installed does not show a "lost communication" as is the case with the old bcm so I'm assuming that there is something wrong with my original bcm. What are your thoughts?

SnowMan01

Oh I also forgot to comment on your second problem. We have two keys for the Montana (my wife's and mine). From what I understand you had a problem with the key? Is that right? In my case both keys have been locked out.

SnowMan01

What is a bypass kit?

RevGTO

iTrader: (12)

The Bypass kit is supposed to establish a direct connection from the ignition tumbler to the ignition module, bypassing the need for the module to recognize the correct key transponder signal. But your problems sound like they go beyond that.

I'm sure at this point you've done some reading on whether used BCM's will work. It seems to me that the evidence suggests that they will not. A new GM BCM is the only solution that I can see to your problems.

WhiteBird00

iTrader: (4)

The BCM in most (if not all) GM models is not reprogrammable. A new BCM is matched to the vehicle during initial installation and it cannot be reprogrammed after that. Fortunately for 4th generation f-bodies, the only programming is matching the resistor in the ignition key (it records the first key used after installation) so installing a used BCM is a simple matter of matching the key resistor pellet - there are only 14 possible values so it doesn't take long to find a match. Newer models were more sophisticated and actually matched to the VIN so transplanting a used one doesn't work.

Your analysis sounds correct. I can see how the dealer might think the action of removing and reinstalling might have jostled or reset something but it is very doubtful that it would happen that way every time you tried it. Besides, if I remember correctly, the BCM is easily accessible in your vehicle - under a seat - so there's not much to be jostled. If they're thinking a loose wire in the harness then why would it only be loose with the original BCM and not with the replacement? Unfortunately, I expect a new BCM will be quite expensive.

SnowMan01

Thanks for your responses RevGTO and WhiteBird00. The dealer has certainly quoted me an expensive price -$500. I have tried to purchase a much cheaper one from other auto part shops in my area but I haven't found a price for much less. I have searched the internet and found some refurbished units for around the $200 dollar mark. Some say dealer programming is required and others do not. I found that a place called rockauto sells it for $169 and states it is an original refurbished acdelco unit and that it must be dealer programmed. I have found others on ebay and amazon but the description of their units are much sketchier. Some say the bcms have been taken out of other vehicles and must be dealer programmed - nothing said about being refurbished. I am quite leery about getting one of those even though the price is much better because I don't want to end up taking it to be reprogrammed and being told it cannot be done, which the consensus seems to be for the one I picked up from the wreckers. Have you guys ever heard of rockauto? If so do you think they are reputable? I don't want to purchase their unit and find it is really not programmmable.

G Atsma

I'm surprised you haven't heard of RockAuto. They are huge in the online parts game. Low prices, YOU pay shipping, mostly Fedex delivery. You can trust them.

SnowMan01

Sounds good to me because you never know who you can really trust in this world. I haven't had to do any car repairs other than maintenance for over 15 years now so the online parts sourcing is all new to me.

SnowMan01

One last thing - before I make the plunge and purchase from rockauto (I am located in Canada so it makes the transaction more complicated paying extra fees, taxes and duties), can anyone suggest what the problem might be other than the bcm? From what I feel in my gut and what you guys have said so far it is probably the bcm. I went out again today and tried swapping the two bcms again just to see if anything had changed. It had not. The big clincher for me is that the scanner can communicate with the wrecker's bcm but NOT the original. I phoned about getting the bcm programmed and was told $100 for labour and a $50 gm programming software fee for a total of $150. This is totally non refundable if this is not the problem so I am a bit nervous. I have even gone so far as to disassemble the old bcm to look for any component which might show signs of a bad solder joint or being burned or overheated. I could find none. I even gave every major component a knock while installed, all to no avail.

RevGTO

iTrader: (12)

Internet diagnosis is a tricky business, but WhiteBird knows his stuff better than just about anybody on here. And it seems like a consensus has emerged that the only thing that explains your constellation of issues is a bad BCM, and that only a new BCM can solve it.

And G Atsma has it right about RockAuto. I can't begin to account for the amount of money I've spent with them maintaining our family's fleet of vehicles - all of which, except the 2009 G8 and 2007 Terraza - have been 2002 and older. Never a disappointment about a part itself or timely delivery.

SnowMan01

Thanks Rev. I agree with what you said about Whitebird. I have seen some of posts in other threads where he really gets into the details - he knows his stuff. Also thanks for the reassurances concerning RockAuto. The only thing holding me back from buying the bcm is that I've thought a lot about all the trouble codes my scans of the ecm and tcm have produced - approx 30 for tcm and 70 or so for the ecm, ALL of them being P codes except for one lonely U 1064 code on the ecm which is about losing communication with the bcm. I previously neglected to mention that a scan of the EBCM (elect brake control mod) produces 5 "C" trouble codes and two "U" codes, U1000 and U1017, indicating loss of serial for class 2 devices"U1017" and malfunction of class 2 data link"U1000". I am wondering why there are so many codes for those scans not associated with the bcm "?". Maybe there is something much more serious going on than just the bcm. All trouble codes are followed with the two digit number 00 which the vehicle manual states that it means no further info is available on the trouble code.
Any further input would be greatly appreciated.