zygee

So I've been having some crazy canbus communication codes and stuff and all the gauges on my dash will drop to 0 i.e. gas/tach/speedo etc. I just did a load/voltage drop test and these are the results (followed by a full list of codes etc.)

27R to 6B .3v
27R to 14B 0v

28R to 6B 0v
28R to 6B .3v

I.e. Red probe on ECM PIN 27 gmlan- with black probe on OBD pin 6










here is the full list of codes that did not produce a cel on the dash, could not be read on torque light, which I read on a maxisys scan tool. All of which went away and didn't come back after deleting except u0073

P0575 cruise control switch circuit
P0856 traction control torque request circuit
U0073 control module communication bus off
P0121 lost communications with abs control module
U0140 lost communications with BCM
U0155 lost communications with instrument panel closer (ipc) control module
C0561-71 system disabled information stored invalid serial data received
U0100 lost communications with ECM
U0101 lost communications with TCM
B0081-71 passenger presence system 1 invalid serial data received
B3031 security system controller in learn mode
B3060 unprogrammed transponder identification code received
B0081-5A passenger presence system 1 plausibility failure
B1025 audio output 1 left front circuit
B1055 audio output 4 right rear circuit
B1423-03 DTC description unavailable

At first it would take about 20 minutes to get the dash acting crazy followed by abs/traction control off, service vehicle soon, and contact dealer notifications on the dash. I replaced the battery and now I don't get the service vehicle soon notification but the others come up.

When this happens the car seems to drive fine but if I turn it off it may or may not let me turn it back on. I turn the key and get absolutely nothing. I unplug the battery for a while and then I can drive like normal, no issues, until it all happens again. It now happens within about 7 minutes or less.

Also worth noting is that this is a manual swap tuned by Pat G and the BCM tuned by Chris White. It had been driving fantastic for weeks. I went to check clearance for 6 pot Brembos on my front passenger side, found it to be good but didn't have time to set it up so just put the stock stuff back.

ABS stuff is all hooked up right.

zygee

Fingers crossed praying over here that everything turns out to be caused by this failing alternator 🙏🙏