posted on Jun, 4 2018 @ 11:52 PM
I'm sure you're already familiar with this site: Nissan Altima Manual
I'm definitely no expert when it comes to working on cars. However, given the operating sequence you report when operating the brake pedal, the
following seems like a simple diagnostic to try that might help you narrow down the problem.
There are lots of diagrams. Many of them appear to be redundant. However this schematic seems to be somewhat applicable:
The stop lamp switch is connected to the fuse block through a 10A fuse #7.
When when the brake pedal is depressed, the switch opens and power is no longer fed to the Body Control Module. So, the default condition of the
switch is closed, meaning that whenever the brake pedal is not depressed, a constant voltage is fed to the control module. This on/off state would
seem to correspond to your experience with the high pitched electronic sound.
If you pull out fuse #7 and the sound stops, that may indicate you have a problem with the BCM. I'd say that probably means replacing it. However, I
would suggest you consult with your mechanic before investing that kind of money in a new control board. Also if you do not replace this fuse after
this test, you will not have brake lights.
It occurred to me that because of the two different locations in the travel of the brake pedal that silences the noise, it may be related to the
cruise control system. A quick tap of the brake pedal deactivates the cruise control, however it remembers the last speed. Pressing "resume"
reactivates cruise at the previously set speed. However, if the brake pedal is significantly depressed while in cruise mode, the cruise control
erases the last stored speed and you have to perform the full setup again.
Hope this at least gives you something else to look at.