H3 BCM Bypass/Delete

[Griff22usmc]

Hey guys. Well my truck decided to activate the anti theft shutdown while on my way home last night. I was doing 50, trying to merge over and than hammer no power. Had to coast into the center turn lane on a highway. Stuck for about 2hrs in rush hour traffic. Even had the cops called to help traffic get around me but they never showed. Onstar had her towed to the dealer. Dealer told me today that there's no communication between the BCM and the rest of the vehicle. They ordered another and will do testing tomorrow to see where the fault or trigger lies.

This is my 3rd BCM replacement in the life of my H3. One was to fix brake lights or something, another was water damage from a roof leak, and now this one. I'm at 97000 miles... 3000 left on warranty. I can't afford to keep buying them.

Has anyone completely bypassed the BCM yet? If not anyone have some insight for me? I would rather get rid of it (as Recon calls it "its the H3s Achilles heel") and go basic with the wiring.

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[5gn-h3t]

Removing the BCM is possible but it won't be a simple bypass. You will be re-wiring the ENTIRE truck. You will lose many of the systems that make the H3 great. Everything from the airbags to the brakes send data to the BCM. I suggest you try to find the root of your issues.

Are you sure you don't have any current moisture problems?

 

[SedonaBound]

Three BCMs replaced tells me that they're being fried by something else that's overloading them; perhaps sending too much voltage or a bad diode somewhere. If the dealer has the data, he should look at the incoming signals that affect the anti-theft circuit. Or get the anti-theft circuit data, a meter, and save yourself a lot of trial and error labor cost. Might be a real PITA to fix.

 

[Griff22usmc]

OK. The moisture problem was a one time event... they said the see no evidence of that. They told me they'll investigate what caused it and fix the root... I have non problem leaving it for awhile at the dealer, so I'll do that again. Last month it was their over 2 weeks for a steering fear box replacement, front shaft and some other little things. I l hope this is the last.... once the warranty is up I'm screwed

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[alrock]

I've replaced a lot on my truck but electrical bugs have not been a part of it. No BCM replacements here.

 

[Griff22usmc]

Yea theirs gotta be a bug somewhere else... hopefully the find it

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[06 H3]

I too have never gone through a BCM *knock on wood* I think most havent so its probably some extreme case and they just havent found the bug yet...good luck hope they find it!

 

[Griff22usmc]

I'll let you know tomorrow after I talk with the dealer

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[ReconH3]

If there is no way to bypass it, my next step is to looking into extending cables, and moving the BCM up to the roof. It's not as simple as it seems. This needs to be done by some electrical pro because the BCM is very sensitive. Cables have to be compensated for extended length and shielded for any interference. Unfortunately I don't know anyone like that in my area.


"Ex Umbris Venimus"

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[Griff22usmc]

I shivered reading that. I would love to move it.. specially being in a flood plane. How does the dealer reprogram the BCM in a replacement? They aren't to expensive, just don't wanna find out how much the dealer will ask to reprogran

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[ReconH3]

That would be a good question for Jerry. You could also see if it's an item PCM for less could get and reprogram. They're in NC so you could even drive up if they need the H3 in person. I was planning on chatting with them about such options. They could be the ones to make a cable extension with male/female plugs so that we could move it ourselves.


"Ex Umbris Venimus"

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[elripster]

Man the BCM is extremely integrated into your truck via hardwired copper and the CAN bus. It's either the gateway between other modules or listens and adds its 2 cents to almost every function. Losing it will likely mean losing ABS, traction control, stability control, as well as the little features like being able to close your sunroof after you key off but haven't opened the door. To take it out is to turn the truck into basically a mid 80's totally analog vehicle with a modern OBD2 powertrain which might not start due to the theft deterrent call and response interrupted by removing the BMS.

I have done a significant amount of work designing custom hybrid and EV powertrains in vehicles with modern electronics and I wouldn't even dream of trying to get by without the BMS even with all of my equipment and even if GM supplied with a .dbc file (so I don't have to reverse engineer the CAN bus).

Relocating it isn't so bad. The green/yelow CAN wires need to be a twisted pair to reject noise but that's literally no harder than twisting two wires. Usually you just put on end in a drill and twist away.

Frank

 

[MUTAINT]

Frank, IF someone (you) could make and sell a BCM relocation kit it would sell like HOT CAKES!!!!:thumbs:

 

[elripster]

I'm drowning in unfinished projects so I won't be able to get to it anytime soon. To add to it we put an offer in on a place so May/June will be shot moving. Maybe if I could get my hands on a wiring harness I could see what is entailed. Anyone know of any junked H3's I could pillage? My H3 is one of the mechanical things in my life that just works every time so I loath to mess with it. There are a lot of contract cabling outfits I might be able to get to make some harness adapter.

See... that's how I get into more projects...

Frank

 

[Griff22usmc]

I'll stop by PCM for less next time I'm in Charlotte, which I believe will be in two weeks.

Update on the my issues: there was a miscommunication on the phone the other day and it turns out the PCM was the unit not communicating. Once they replaced it, they got a code saying their was a fault in the ignition circuit. The problem was a shorted wire. The wire was the clutch neutral switch. Apparently doesn't matter what transmission you have, all the wiring is under their (I have an automatic). The wire shorted out on my ebrake bracket. Jerry (local hummer owner) works at the dealer and handled the problem personally. Pretty awesome service.

Count me in for a relocate kit.. if it happens plz

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[ReconH3]

Relocating it isn't so bad. The green/yelow CAN wires need to be a twisted pair to reject noise but that's literally no harder than twisting two wires. Usually you just put on end in a drill and twist away.

Frank

Hi Frank,

Thanks for the useful input. Looking at pics of the BCM, it seems like there are more than just the two CAN bus wires. Is that so in all the models, or only in the older. pre-CAN bus BCMs? I'm thinking that all the cables that come from all the sensors and lights, each has it's own pin. I have no experience with this, so please correct me. TIA

 

[ReconH3]

Fortin PSLOCKSL2 Passlock II Data Bypass Kit for Hummer H3 Vehicles

Would something like this help bypass the BCM security and avoid shutting down the vehicle if there was a BCM failure? I'm aware that you would leave your H3 vulnerable to thieves. What I was thinking is programming, then removing it, and taking it along as a backup. If the vehicle shuts down, you plug this in, and drive off. Just thinking out loud. I'm very much electrically ignorant, so please help us out. TIA

 

[elripster]

Pretty much all OBDII vehicles have 2 CAN buses. There might be an exception out there somewhere but I have not seen one. One is a 500 kb, high speed bus, that handles the time critical powertrain functions. The other is a 250kb bus that handles the less time critical stuff like warning lights, radio, etc... Often only the green/yellow combo is present in the OBDII port. They have signals that the BCM is shrink wrapping.

That data bypass might just do the trick but I wonder if it will still allow the truck to run if the BMS fails altogether?

Frank

 

[Steve #1]

The BCM controls to much to consider removing it.

The thread seems to have morphed a little and I'm guessing the main reason is concern of the BCM getting wet. Waterproofing of electronics has made major advances in the past year. The industry is aimed mainly at mobile phones now, but there is no reason you couldn't have a BCM or PCM done. http://www.hzoinside.com/ There is another company with a very similar process that is aiming more for the post consumer market, but I cant remember their name.

 

[ReconH3]

Wow. Great info. Thanks. Can I send them my whole H3 to have waterproofed? Just kidding. Sending out ECM/TCM/BCM would be a good way to help these issues. Thanks again.


"Ex Umbris Venimus"

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[06 H3]

If that is a solution that will work I plan on doing it....it would give me a piece of mind if that mudpit is deeper then you think

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[ReconH3]

If that is a solution that will work I plan on doing it....it would give me a piece of mind if that mudpit is deeper then you think

That's exactly the way I think. I avoid water at all costs, but you never know when you may have to.



"Ex Umbris Venimus"

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[elripster]

Waterproofing these boxes makes a lot of sense. You can only move them so high and if it's not enough...

 

[Nacho]

The BCM controls to much to consider removing it.

The thread seems to have morphed a little and I'm guessing the main reason is concern of the BCM getting wet. Waterproofing of electronics has made major advances in the past year. The industry is aimed mainly at mobile phones now, but there is no reason you couldn't have a BCM or PCM done. http://www.hzoinside.com/ There is another company with a very similar process that is aiming more for the post consumer market, but I cant remember their name.

Liquipel is another company that has a waterproof coating for cell phones.
[video=youtube_share;jedv15ov3sw]http://youtu.be/jedv15ov3sw[/video]

Their website :link:

 

[MaxPF]

Fortin PSLOCKSL2 Passlock II Data Bypass Kit for Hummer H3 Vehicles

Would something like this help bypass the BCM security and avoid shutting down the vehicle if there was a BCM failure? I'm aware that you would leave your H3 vulnerable to thieves. What I was thinking is programming, then removing it, and taking it along as a backup. If the vehicle shuts down, you plug this in, and drive off. Just thinking out loud. I'm very much electrically ignorant, so please help us out. TIA

Easiest way is to have theft protection turned off in the ECM/PCM. I would only do that if I had other theft protection installed though. As a rule, that kind of failure is so rare I would just leave it alone.

Pretty much all OBDII vehicles have 2 CAN buses. There might be an exception out there somewhere but I have not seen one. One is a 500 kb, high speed bus, that handles the time critical powertrain functions. The other is a 250kb bus that handles the less time critical stuff like warning lights, radio, etc...

I don't know about non-GM vehicles, but 06-07 and up GM vehicles only have the 500kbps high speed GMLAN (twisted pair CAN) and a low speed single-wire data bus. Earlier vehicles just used the single wire class 2 data link. Medium duty vehicles with CAN busses all use the standard J1939 250kbps CAN.