Hello. I am working on getting a test bench set up so I can reprogram different GM modules. So far i have  BCM, and Radio communicating and am trying to get DPS to communicate with HMI. I have HMI hooked up to radio through the MOST bus. But hmi still does not want to speak. BCM is address 40 and radio is 80. What could i be missing? Do I need to hook up IPC and radio controls as well? I got all the wiring diagrams from gmupfitter. Truck is a 2015 Silverado. This is all for fun and learning new stuff. Have to keep my mind working, turning 60 this year. Troy you've set up a test bench, any tips? 

Thanks Dom

Test

IMG_2792.HEIC

For the HMI 2.5, all the units must be on the MOST line, IPC, CD drive, HMI, Radio, and BCM. The MOST loop must be closed. I don't know how to close the most loop without adding all the modules that's on the most line.

The BCM module is the one who gives the orders if the HMI should speak or not, via the 'Serial Data Communication Enable' wire.

The HMI must be connected to the MOST line, the BCM connected to both the high and low can bus line, and the Serial Data Communication Enable wire must be connected to the HMI then to the BCM. 

Without doing the above, the HMI will not show on the High speed canbus.

 

Here are the diagrams.

Look for "Serial Data Communication Enable wire"

 

Serial Data Communication Enable wire Pin 5.

K74 Human Machine Interface Control Module X1 .pdf

 

 

Serial Data Communication Enable wire pin 23.

K9 Body Control Module X4 (CZ2) .pdf

you can just connetc the missing loop parts i have a insignia b facelift ipc in my car just pull out the loop wire and short them gm has service cabel for that