BCM communication!!!!

Hi guys I'm back with yet another question...... put a 2008 6.0l with the 6L90 trans in my old chevy all is well except the trans. I can't get any of the inputs to work (tap shift tow haul)! so I figured if I use the BCM from the same truck which controls this then problem solved.... not so! when I hook up my scanner I can actually see the changes I'm making by pushing tow/haul button in the BCM but when I look at the trans data it does'nt change? When I bring up the info in the proccessor (serial#,OS,etc) there is a line that has BCC is this supposed to be the BCM? cause if it is then it's blank! I'm wondering because I turned all the BCM dtc's off it won't communicate? The ECM, TCM, and BCM are all from the same truck no harness has been modified. Without these functions when I tow with it it's always hunting between 5th and 6th gear (big load) and I'm concerned that over time I'll wreck the clutches.
Thanks:shrug:

dont need a BCM... run a Corvette tune and set it up the same and will work fine

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Originally Posted by Doubledip

dont need a BCM... run a Corvette tune and set it up the same and will work fine

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Isn't the tap up/tap down shifting direct wired on a corvette or so I've heard(on this forum I think).

Well I tried that.....no dice! Maybe I don't know how to program the tranny separate! I don't know how to just change the TCM. Did anyone on here do this on a 2008 6L90E? Any help would be welcome cause I still can't get it to communicate.

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Originally Posted by 53mercury

Well I tried that.....no dice! Maybe I don't know how to program the tranny separate! I don't know how to just change the TCM. Did anyone on here do this on a 2008 6L90E? Any help would be welcome cause I still can't get it to communicate.

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Awe fark. That's generally from an input that isn't supposed to be there or there's one missing. Essentially the BCM needs everything to work that it had on the donor truck, such as ABS, and Speed Sensor Inputs to relay every signal correctly :(

I,m thinking the same cause it is missing ABS,door switches, etc! funny thing is though that it doesn't trigger abs codes (in the BCM)! only codes I get is door switches! I am wondering that because I turned the "U" codes to not turn on the engine light would that stop it from communicating????? If I could get this to work I would also gain cruise control which I presently do not have.

Man I've tried everything with this even a complete re-write! Maybe GM tech II ? I wondering if it's because I did a complete write without the BCM there to get past the vats... And now it doesn't reconize the BCM!!!!????? Any thoughts out there on this... Very frustrating !

Any thoughts IDRIVEAG8GT ? You've been very helpful to me before !!!

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Originally Posted by 53mercury

Man I've tried everything with this even a complete re-write! Maybe GM tech II ? I wondering if it's because I did a complete write without the BCM there to get past the vats... And now it doesn't reconize the BCM!!!!????? Any thoughts out there on this... Very frustrating !

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Post your tune and we can take a look at it. :)

Hey guys hope your still sticking around I've been away for a while but here is my tune file..... It is supercharged and having the tranny control would really help !!! I also need to do more tuning on the shifting it bogs for a second when I hammer on it and I think it's the torque management.

Did you make any progress with this? I'm about to swap a LY6 6l90E and would really like to have cruise.

Mike

No actually I haven't been busy so not a top priority right now but I would like to cure this annoying problem! Maybe it's something I need GM's tech II to cure....not sure. I know it is on the can bus for sure cause I can see the info on my scan tool but for some reason the PCM ignores it!??!

I read somewhere else that you flashed a corvette program trying to get the corvette style tap shift inputs to work which are hardwired to the trans instead of the BCM like in the trucks. Have you put the truck program back which will look for the truck BCM?

Mike

Couple things that may help out ...

Cruise Control - the E38 is not set up for this functionality. If using an E38 ECM you will need a BCM for cruise control. Some E67 ECMs have the cruise control functionality incorporated.

Tap Shift - if you are using a truck wiring harness you will need to add a pin / wire to the T43 TCM connector (pin 7 - not used with trucks) to use a TCM Corvette calibration and a hard wired Tap Shift input. This also requires a Tap Shift switch (control box) available from SpearTech. You could make your own if you have schematics, and are comfortable soldering several resistors in series / parallel.

To use a BCM (i.e. have the ECM recognize its presence) you will probably need to enable the VATS in the ECM tune (its disabled in the tune you posted), then use the Relink VATS function in the software. Just thinking out loud - have never used a BCM with an E38 in a conversion.

I have spoken to John from Speartech quite a few months ago about the tap option on the 6L90 and he was saying they haven't got tap up/down to work on these trans either! they are working on it. Do you know of anyone that was successfull with this? I am quite confident in my wiring skills for the resistors and have tried running the proper restance for the corvette but I don't know if I used pin 7 or not I'll have to check. It did'nt work! The real kicker would be to get the BCM to communicate that would give me tow/haul as well as cruise control which is as you stated controoled by the BCM. I did do a write entire but did not relink the VATS.......maybe thats it! I'll certainly try enabling the VATS and relinking!!!! Thanks for the info.

I am running all the 'stock' programming and controllers out of the same unit BCM, TCM, ECM all from the doner truck. I have no idea how to flash a corvette trans tune into my TCM! when I edit anything weather it'd be engine or trans there is nowhere that I can see to change the calibration! how do you put the corvette cal in the truck???

The BCM has to be powered up correctly I don't have the diagram handy right now, but check out the pdf at

http://944hybrids.forumotion.com/t13...-modifications

It shows the wiring required for the BCM, cruse and tu td

Yep all wired up correctly..... it is live and I can use my diagnostic tool (mac mentor) and actually watch as I hit the TU/TD and cruise buttons and see the data change in the BCM but it still won't communicate! I used a GM service manual to wire it as I have the correct cd for the model year.

Still baffeled by this! Was in contact with John at speartech again and he says that he may have a different OS that "MIGHT" work..... but I don't want to take the chance and loose the info "file" I have now. MIKESZ did you have any luck with yours?

I included the bcm in my ly6/6l90 swap. I needed it for the low speed data lines to communicate with the stock gauge cluster. My bcm was not from the same vehicle and is not linked to the ecm/tcm.

I have successfully wired the Tow/haul switch and partially wired the TUTD mode but I have not been able to find the schematics for the truck switches showing the size of resistors. But after playing with it I can get it to go into TUTD mode when shifting to the correct range and applying 4K ohm resistor to the TUTD circuit.
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The Tow haul switch is just a momentary ground switch. I assume you wired it to the correct bcm pin but if it is not working your GM lan high speed data lines are not communicating with the ECM/TCM. You need to have the Gmlan signal going into the BCM and out of the BCM, then it should be terminated by a 120 ohm resistor. I recommend you put you DLC after the BCM to make sure it is communicating correctly.
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Awesome I think I may have made a mistake here ! So I understand the GMLAN schematic and I'm assuming it's terminated inside the ECM with a 120 ohm resistor but I do not see a 120 at the datalink I'm not using the VCIM but that should'nt matter. I will however check and see if I have the LAN correct or not. Thanks

Great info I'm gonna cheak the can routing and see if I have maybe made a mistake on which module goes where in the system.
Thanks

Checked wiring of the can bus on the weekend.......all wired correctly so I tried putting a 120 ohm esister after the BCM....still no change!!! I just don't get it.