It probably is coming from the steering column - where the column passes thru the firewall there is a grommet which gets dry and squeaks when the wheel is turned. The easiest way to stop this squeak is to lubricate this grommet - either from under the car (best method), or spraying WD40 over the general area under the brake master cylinder. You may also be able to spray WD40 using a spray tube from inside the car if you push the carpet out of the way. It's better to use a longer lasting oil than WD40 by the way.
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