“Service transmission Now, unable to shift soon” message on 2021 Tahoe

[West1]

That is garbage.
All the modules store history codes..they could at least look.
Next time take a picture or a video of the code on the screen...harder to argue w/ evidence.
These dealers are really starting to tick me off...

I did take a picture and a video.
This morning it happened again and I drove to the dealer and kept the engine running. They scanned it and said there’s a ton of codes popping up with a low battery voltage. They said start with replacing the battery and go from there.

I also asked if I could swap the battery myself (since not a lot of people on the forum know the solid answer) and they said yes, no problem swapping batteries.

Off to buy a battery…

 

[WalleyeMikeIII]

I did take a picture and a video.
This morning it happened again and I drove to the dealer and kept the engine running. They scanned it and said there’s a ton of codes popping up with a low battery voltage. They said start with replacing the battery and go from there.

I also asked if I could swap the battery myself (since not a lot of people on the forum know the solid answer) and they said yes, no problem swapping batteries.

Off to buy a battery…

FYI, Low Voltage has also been caused in GM vehicles by corroded frame ground wires...so, make sure you/they inspect those bonding braids. (I will never understand why GM thought bare copper braid for frame ground in a corrosive environment was a good idea). This video is worth a watch.

 

[Fless]

FYI, Low Voltage has also been caused in GM vehicles by corroded frame ground wires...so, make sure you/they inspect those bonding braids. (I will never understand why GM thought bare copper braid for frame ground in a corrosive environment was a good idea). This video is worth a watch.

After having watched that video a few weeks ago, I wondered if the SUVs have that same ground cable.

 

[Doubeleive]

After having watched that video a few weeks ago, I wondered if the SUVs have that same ground cable.

not only that but the idiots put the ground cables right where all the water splashes up from the wheels
job security I guess, some engineer needs a smack upside the skull

 

[West1]

Update… my battery was the issue.
I swapped it out (scared af after reading on our bus bars & ECM stuff) and have no issues atm!

(Can’t load pic, says file is to big).
I was worried disconnecting the positive wire would cause ECM issues but… I was the test. There’s a small bar near the negative terminal that needed to be removed, a clip with a red tab and a clip on the bus bar housing that holds it on the battery.
After this, there’s a big bolt at the bottom back corner of the positive terminal that unlocks the physical battery. Once that’s done, it’s easy to loosen and remove the battery.

I figured I’d mention this since there seems to be little info on people removing the battery on our rigs.

 

[Tahoe14]

You do have to be careful with these new rigs changing batteries. One little spark and it can throw a code that the Dealer has to clear. Unhooking the negative battery cable does not always work.

 

[StephenPT]

After having watched that video a few weeks ago, I wondered if the SUVs have that same ground cable.

Nope - '21+ SUVs use a cable with sealed heat shrink ends and wrapped in Tesa tape. Pretty weather proof in my book. I saw the SMA video when it came out and removed by fender liner to check.

Part number # 84871178