[jmoney1le]

First post here.
I have a 2020 2SS 1LE. just turned 3000 miles about 2 months in from new. While warming up car for my drive home from work one evening (after dark headlights on auto on), I noticed that all of my instruments stopped working (analog gauges went to 0 position) and the center of the instrument display started scrolling through alerts for almost all of the systems that it can report (low fuel, service suspension, service diff etc.). The headlights would go out and come back on while in auto default mode at random (scary while driving backroads at night). The Hvac system goes to full hot and full speed fan blowing out of whatever vents had been previously selected. HUD shows 0MPH low fuel (I usually have it in track mode style). Starting and shutting down the engine can be temperamental as well. Sometimes starting and shutting back off. and sometimes requiring holding down the button 2-3 seconds for the engine to stop. Disabling the auto headlight system by rolling back the headlight knob makes everything go back to normal. turning on the parking lights or headlights in any fashion makes it come right back. Sometimes the car will act normal on cold starts but always starts acting up again within 10-15 minutes of running/driving. Car has been at the dealer for a week now. They ordered and installed a BCM thinking that was the problem, but I was informed that didn't change anything. I have dug around the internet quite a bit looking for any complaints of something similar but without any luck. Has anyone seen or heard of any similar problems, and or solutions??

[arpad_m]

the the forums, jmoney1le.

My hunch is you need a trip back to the dealership and show them technical service bulletin (TSB) 20-NA-055: https://static.nhtsa.gov/odi/tsbs/20...81687-9999.pdf

[jmoney1le]

Interesting. Car is still at the dealership. I will be sending this along to them. I'm sure they have access to all of these things but I want to help speed the repair if possible, and educate myself for what may be to come after warranty expires. Thanks for the reply.

[arpad_m]

My pleasure, let us know how it panned out

[jmoney1le]

Update: I called and asked the service writer to check with the tech working on my car about the service bulletin. Car came back after 8 days at the dealership. I was told that the problem ended up being a short in the rear proximity sensor module. Apparently the short in this module threw the main BCM into limp mode causing all of the crazy behavior. I have had the car back for about 1500 miles of driving now with no further issues.

[arpad_m]

Interesting, what were the odds... Thanks for reporting back, and if it was fine for 1500 miles, the issue does seem to be resolved

[Dexterpoole2014]

when you told them about the service bulletin did they try that or did they disregard it?

[xplct]

Had the same issue with my 2020 tahoe. The dealer fixed it over a weekend.