For the last few weeks, my car has made a high-pitched whining noise, especially while idling. I ignored it.

Then today my car showed a check engine light and code 84 (“limp mode”). I couldn’t drive it anywhere until I turned it off and on a few times.

I took it to a mechanic and they said it pulled the following codes:
P0651
P0641
P0697
P06A3

They told me we need to replace the alternator and drive belt, and it would be $890 (in Nashville).

1. Is there any way these codes relate to an alternator? The internet said it’s just a computer thing that needs to reset.

2. If it is indeed an alternator, am I getting ripped off?

 

the codes ...all of them set when the ecm detects a short to grd or voltage on the 5 volt reference circuit.
typically this problem would be wiring or a bad ecm.

if the noise is coming from the alternator...you need an alternator. If the belt is worn or glazed you need a belt. If you asked the shop to find the source of the noise...that is what they did. the dtc seem unrelated.

they will charge you diagnosis time maybe 1 hour + parts+ part replacement time 1 hour labour.