Sometimes it is just a bad battery

There is no mutual exclusivity. They are interdependent in many ways.

I'm not saying it's done out of malice, but incentives drive behavior. You'd probably only develop solid diagnostic chops in the shop if the shop placed "bids" on fixing an undiagnosed problem, betting they can figure it out & fix cheaply.

One reason is turnover in dealer mechanic staff. Independent specialists tend to be more stable and have a genuine interest in and affection for the older cars of a particular brand.

Another reason is that most new luxury brands are highly focused on leasing brand new cars or getting customers to trade in on the latest model. They really only want to sell brand new cars at the top of the depreciation curve. People who own older cars will usually not buy them from the dealer and tend to not use dealer mechanics (often because the dealer is the most expensive option around). So dealer mechanics see less older cars, and service managers largely don't consider owners of older cars to be good/profitable customers that they need to keep happy.

A related issue that causes poor experiences like you describe is the "book time" job scheduling/pay system used by most dealer mechanics. This system favors a "parts swapping" approach where mechanics try to fix problems by quickly installing new components with a minimum of diagnosis time. This gets expensive for the customer due to dealer parts costs and strongly disincentivizes thoughtful, time-consuming diagnostic procedures and research. There is also usually an informal seniority system in dealers where the senior mechanics will take the easy "gravy" jobs that can be completed quickly but cost a lot. Junior mechanics will get stuck with the difficult, hard to diagnose jobs that suck up a lot of time and reduce a mechanic's earning potential. So you end up getting the least qualified mechanics working on tricky, unprofitable issues like yours.

To be fair, these issues aren't exclusive to high end vehicles, but they are especially noticeable at this market segment.

Sure there are experts in every field who really know their stuff, but 95%+ of the people we run into day-to-day just aren't that good at their job and don't pay much attention to what they are doing. So with a bit of research, experimentation, and logic, we can figure out stuff that should be other people's job that they can't seem to do. (... but the average software engineer probably isn't any better ;)

Already there are tools that do most of the basic ODBII functions, but some brands are bad about hiding away specific codes in $50k+ tools as a way to extract money from shops and funnel customers to the dealers.

In the very early days Apple Store has a similar internal system where Genius gets to report and share these sort things. I think it was written by an employees as well. Pretty sure now that thing is gone.

Just search for ISTA-P, ISTA-D, INPA, E-SYS and realoem, TIS, ETK for parts (you can get them for free* too)

If your voltage is steadily above 13.8, then your regulator/rectifier is fried. Swap it out before it starts cooking your battery.

It turned out that one of the battery _cables_ was bad; enough corrosion had built up under the insulation that the voltage would do all kinds of strange things depending on the exact load on the system. $20 for a new cable fixed it all.

Instead, it may have just been a direct, low-level interaction between the battery and the CPU — with the CPU saying “I need more power!” and the battery replying with “she canna handle any more, cap’n, she’s gonna blow!”

(Or more literally: the battery being unable to supply the spike voltages the processor needs in order to boost, and so the CPU’s VRMs noticing that the boost “isn’t working” [by getting browned out] and signalling the CPU to stop trying. Or, alternately, the battery heating up when trying to provide that power, due to increased internal resistance, to the point that the heat so produced, triggers thermal throttling in the CPU. Either way, a CPU that couldn’t get its highest frequency-scaling multipliers going for more than a few milliseconds before stalling and dropping back down. Which would tend to feel slower, and lead to lower benchmarks.)

Sure, wait a few days since I am getting a new phone. Spent ~$80 in what is probably the crappiest no-brand Android I could find in Amazon with questionable preinstalled software. Cleared it with IT and that's what I use to test my work-related stuff.

In my location they could not fire me for requiring a phone for my job-related work, but didn't want to make trouble for $80, specially when I was already fighting for my holidays (a much more important thing for me).

Some of the corporate phone stuff will require a passcode of a certain length. When I was in this position, I had two phones, but the corp phone stayed in my bag, mostly off (would use it for tethering for work incidents when out of town, and as a backup 2fa device), and I ran corp email on my phone until it got too ornerous (outlook for android ate my battery life and/or was impossible to auth with); then I only checked from the corporate laptop, but outlook for macos would drain my battery in standby, so I couldn't leave it running and forgot to start it.

OTOH, I was established with seniority, so I could do whatever. I'm not sure a new hire could do whatever; especially outside of my group where we didn't really accept the corporate norms.

If you need some applications installed on a smartphone in order to perform your jobs duties, the smartphone is a work tool. This must be supplied by the employer if requested. In practice, our company offers two choices if your position requires this.

For one, you can be issued a company owned and managed phone. This phone is registered with the MDM and the MDM manages the installed software. Additionally, because the MDM can wipe the work phone after loss or theft, company data may actually be stored on the phone. The drawback is that you now have two phones.

Alternatively, there is a small number of use cases authorized to be done on personal phones with basic security enabled. For example, access to mails with a web browser, an authorized messaging client, or a TOTP MFA application, like google authenticator. These are fine, because they either don't store company data on the phone, or because they are not critical on their own. You can have my MFA token generator, because you don't have my password, for example.

So for example, personally speaking, I have to have a TOTP app around, a messaging app - threema for work - installed due to on-call and maybe duo in the near future. I consider those reasonable, especially because I have a TOTP app and something for oncall anyway. Or used to. RIP Firealert :( However, once I'm supposed to install teams, outlook or some of these, I'd balk.

That's just what LiPo batteries do at end-of-life. Not specific to Apple by any means.

Based on your experiences, I am going to assume you are not in the same situation. You will likely have better results for an otherwise identical request.

Have a good day.