How long could it take to re-write new code? Um... anywhere from weeks to never. You're talking a global corporation here. They probably have a special software 'Team' somewhere ...might not even be in the U.S. ..probably India, ...which they write code for all vehicles present and in the pipeline. So... ya need to fill out a request form to get an 'estimate' for the labor hours and costs for the 'fix' from the software team, Then submit the paperwork along with a justification to management to see if you can 'sell it' & get it approved. Oh wait, that boss is on vacation for 2 weeks. It could fall dead right there. Hopefully not. If approved, send the project back to the software team and get in a cue. Chances are the team is working on lots of other 'fixes' or new product software. They've experienced budget cuts so it takes longer...lol.
If the person in charge of the update is really aggressive, or an effective employee (like maybe 15% really are), Billy Bob in Detroit might call his buddy who runs the software team directly and goes something like,
"Hey, Rajj, how's it going? How are the kids? Hey I got this discharging issue that's kind of critical. Lots of riled-up truck owners and dealers all over my back-side on this one. ...I know you guys are up to your eyeballs in alligators, ...but do you think there's any way to slide this project in a little faster?" Rajj likes Billy Bob because they see eye-to eye. They shared common company-bashing over drinks at a training event a few years ago. The usual things: Overworked, Under-appreciated, Not enough pay, Boss is a real jerk, Will our team get moved somewhere else? etc. Rajj agrees with Billy Bob this is important & instructs his guys to get on it right away, and his team gets the software re-programming done fast. Rajj calls Billy-Bob back,
"Hey, you owe me some of that good ole Michigan Cheese for this one! We got your 'fix' done, I'll shoot it over to you this afternoon buddy!! Tell Frank over there he's still a jerk and owes me $20 for that card game I whooped his a$$ on! LOL". This is where relationships matter.
OTOH, If you have a new dufus handling the job in Detroit, who's more worried about the latest CBD products or the high potency THC gummies his buddies are IM-ing him they're going to all use up tonight ...and he's obsessed with the latest posts on his online gaming forums, ...yer in trouble. He might not be the guy who'll ever get that new programming plane off the ground, so to speak. Everyone knows he's a dud and should have been cut-loose 3 years ago, but his boss Melinda has 3 teenage girls herself and is sympathetic to his psychological needs. He ain't going nowhere. He just needs the right environment. He might even get promoted over hungrier, more competent workers. He'll spend 4 days sending off 15 emails when one 5 minute phone call would have produced immediate results. So, it could sit there dormant till enough dealers squawk loud enough it gets put on someone else's desk. Even then it might just sit in line till 'whenever'.
Once the code actually gets re-written, then the protocol is to probably send the code off to the 'testing team' to try out and ensure it works. That might be virtual, or an actual test truck -- which again, get in line...
"we've got other things we're working on".
"Dave over there has been on my rear for weeks with a red-hot-poker to finish this long-term testing for a 2026 prototype ...once we get that finished...." An effective employee will pick up the phone and talk to someone (GASP!!) get it moved front and center. Cause it's critical. But these days most employees won't do that. They'll spend 2 weeks shooting emails all over the place with little effect that get lost into nowhere land. Sometimes ya fix one issue and these computer nerds completely overlook the obvious and create a new problem that any normal person with half a brain would have spotted and resolved before sending the new code out in the first place. Some new girl who's 3 months out of an internship with a bank IT department, who has no clue debugging automotive code (sorry ladies ...could be a guy too). ....and now the whole process has to start over again to get re-fixed.
It's not like a small company or in the old corporate days where you could walk down the hallway to the programming team, knock on Jim-Bob's door, BS for 2 minutes about his latest fishing or hunting trip, tell him what you need, he hands your request to his low-language-and-social-skills programming guy there ....and you continue on with the hunting/fishing stories while the programmer taps away at the computer. Then he's done. Jim-Bob's been through the drill a few times and asks his computer guy if he double-checked for this or that ...and the other...just to make sure there weren't any other problems he'll get blamed for. The programmer looked it over again, ...and after reassurances, he hands you back the 5 1/4" floppy with the new 'fixed' code. You can take it to the testing guy on floor 2 before lunch, and he finishes the testing by Fri, exactly when he promised he'd have it done. The testing guy's an old-timer who knows his crap and knows it's right when it leaves his dept. Then it goes out to the dealers.
Obviously the above is humorous conjecture. But having worked at a global corporation that's how it kinda works. Eventually things get done. Hopefully it's critical enough to get finished soon. But DO investigate other possible 'discharges' in case it's something else.