Hey everyone I'm at an odd place in the project truck I am building. Its a 1965 C10 on a trailblazer frame, with an LS2 running on a Holley Terminator X Max. The 4x4 is intact still except the wiring for it, I am making the harness right away but the big issue is how do I wake the TCCM up without the rest of the factory components like the BCM? Does the wake signal originate from the BCM? I haven't done any class2 sniffing or anything, will I end up with an arduino and OBD shield to wake it? Or maybe an original BCM installed also just with power, ground and class2 hooked up, wonder if that would work? I obviously do not have a class 2 data source running the Holley.
Wiring a 4wd system in a swapped vehicle, Class2 data issue.
- Thread starter CrankyB
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Mooseman
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Need to double check but I'm pretty sure the Torsen transfer case from the SS is not controlled by any TCCM since it's a real full-time AWD. There may be a speedo sensor. And it would also be better suited for the type of power the LS2 will be putting out.
That would be great! thanks for your help, I would need to come up with the code
I hear what you are saying, I want to try with the 2 speed, it will be in 2HI 95% of the time then 4HI for playing around, and possibly 4LO if I feel like breaking things,
I have cobbled together portions from here and there and built a circuit instead of using a shield or other such manufactured device. I'm currently just fiddling with it as I learn more.
Any module of the Trailblazer can wake the network but it is the BCM that is the Power Mode Master (PMM) and sends the "power moding" messages that the rest of the modules use to know when to operate and when to sleep. These Power Moding Messages can be spoofed by the Arduino.
"Spoofed" means I send the message with the header indicating the message is being sent by the BCM. There is absolutely NO security verification of a message sent on the Class II serial data lines so you can basically send whatever you want. So I can have an Arduino send the Power Moding message that would be sent by the BCM and all recieving modules take the appropriate actions.
For example, even when I have all four 12 volt supply and signal wires to a PCM replicating the key being in the RUN key position, if I send the power mode message that the BCM sends when the key is turned to OFF the PCM shuts down and stop all communication.
No CANBUS,,,, CANBUS is a different protocol with different wiring and different message structure.
The TCCM we use uses the protocol SAE J1850VPW, NOT CANBUS which is ISO 15765-4.
Something else we do not know is what does the TCCM need from other modules? And does it actually need these things or not? And do other modules use what the TCCM sends out?
In our TrailBlazers every transmission shift is announced on the serial data bus by the PCM. And the TCCM receives these messages and sends an acknowledgement message for them. What it does or does not do with this data I have no idea, but I see the messages.
I also see that the TCCM announces the status of the transfer case. 2Hi, 4Hi, 4Lo are all reported periodically. And the PCM and EBCM acknowledge receipt of those messages
Is this chatter needed? I have no idea other than to think "if it wasn't used why would they even program them thay way?"
I hear what you’re saying for sure, I wonder if it’ll be as simple as sending a wake up command and that’s it. It would be awesome to use an Arduino and the send a wake up command and a sleep command to make the systems work outside the original vehicle. I have a couple TCCM and a BCM on the bench with my Snap-On verus edge, im going to play around and see what I can come up with.
Does this scantool display the actual messages on the bus? Looks like this below.
I have made some notations in the image.
Note that the TCCM is not alive on the network at the start of the picture where so many other modules are active Only after a power mode message from the BCM does the TCCM become active in the network. There is some more to it but this is a start.
Here is a short video where I have a DMM connected to the transfer case shift motor position sensor. You see the voltage come up when I open and close the door and then quit after 20 seconds.
The TCCM has battery power at all times. There are no switched power supply connections so it does not matter if the key is on off or whatever.
In the video all I do is open the passenger door and the TCCM activates and sends power to the position sensor showing that the TCCM is indeed active. But that power goes off after 20 seconds, likely because it has not been instructed by the BCM to remain awake. The BCM does this when the key is turned.
I have seen some modules stay awake even after the BCM instructs them to go to sleep, but this only happens while I have some communications going on with the particular module. Like if I have an app reading live data from the PCM it stays awake and communicating even after the key is off and the BCM has issued the sleep power mode message.
photos.app.goo.gl
The TCCM has battery power at all times. There are no switched power supply connections so it does not matter if the key is on off or whatever.
In the video all I do is open the passenger door and the TCCM activates and sends power to the position sensor showing that the TCCM is indeed active. But that power goes off after 20 seconds, likely because it has not been instructed by the BCM to remain awake. The BCM does this when the key is turned.
I have seen some modules stay awake even after the BCM instructs them to go to sleep, but this only happens while I have some communications going on with the particular module. Like if I have an app reading live data from the PCM it stays awake and communicating even after the key is off and the BCM has issued the sleep power mode message.
New video by Thomas J Baker
photos.app.goo.gl
