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Discussion Starter · #1 · (Edited)
I have a 2007 GMC Sierra SLT 2500 HD, having issues with the cab bus issue on both networks.

It all started one day when I was driving down the road and I turned on the AC and all dash gauges pinned all down to there starting position (bottom left) got codes for no communication for BCM, HVAC controls, IPC and many more but they all were from BCM group of modules. So I checked powers and grounds didn’t find anything I didn’t like, tested alternator and battery’s, tried hitting every button in cab to see if I could get it to crash and I couldn’t.

Few weird things I noticed was the rear view mirror was lit up green as normal and all the buttons worked but the digital read out for the temperature doesn’t work, which it never has I believe but checked connection it seems tight and no backed out pins. I even took it apart because I remember hearing an issue with a solder point coming undone on them but this one wasn’t the same board(which I believe is because this year truck doesn’t have the passenger presence system, the air bags are always on, which threw me for a loop, I’ll explain later) Also sometimes my heated seats don’t work when everything else seems to work fine.

I also am getting a code for no state of health from module and Class 2 shorted to ground so I spend the first couple days pulling seats and center console to find the PPS and the wire and learned the hard way that it doesn’t have one so I’m thinking my matco scanner just wasn’t updated to have the correct info and thought it had one but still looked at all the wires and didn’t see anything cut up besides one that had some wear on it and I patched that one up and moved on to splice pack SP205 where they all connect to go to DLC and used the pin each one in till the network goes down and since it was a intermittent issue I only got it to crash when I wanted to one time and that was when I connected the IPC to my homemade Comb tool in 205 but at that point I already had 7 modules plugged in so I went ahead and got a new instrument cluster panel and it seemed to fix the issue for a few weeks

This morning it started doing it again and I plugged in my scanner and it was reading no modules at all which is different from before because before I could always talk to the ECU and TCM and now it switches between the two issues for no rhyme or reason, key on or key off, charged the battery’s all the way with battery charger would still do it, so I hooked up my one channel scope and pin for the bcm group (pin 2) and I’m reading from 0.3 to 2.4 in a wave length pattern I’m new to data bus but it looks pretty uniform and pin 14 that goes to ecm, glow plug and TCM is from 2.39 to 2.4 in a wavelength pattern but a lot smaller spikes and looks more unpredictable, checked for ohms for the resistors and the 60ohms so I’m at a loss of where to look next possibly look into the short to ground on PPS but don’t know how it would know that if there is no module or possible run through the battery cable and main power wires again and grounds to see if I missed something

Any ideas would be great, thanks.
 

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If you look at this video, you will see what normal and abnormal communications look like on CAN HI and CAN LOW.

 
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