How to fix C0035 and C0036 error codes for Chevrolet Uplander 2007?

Looks like it is your front wheel speed sensors. There is nothing you can repair, they have to be replaced, they are responsible for your ABS and maybe traction control (if you have). You can drive like this, it is not harmful to your car, but ABS won't work. The sensor usually is not being damaged (if not physically hammered), usually it is wire which is being turned left and right every time when you decide to change direction for god knows what reason :D

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If you are curious - it is a sensor behind a wheel, behind a brake disc, attached to your wheel hub, aiming on a toothed disc that turns together with your wheel.