I've got this light on the right side of the dash like the traction control light that stays on. My neighbor ran a scan on it and it comes up C121D. Anyone know how I can fix this problem. The day before the light came on I had started the truck and cut the wheels to the right to inspect the front struts, the next day when I started it the light was on

 

Brake pressure code...... Too many possibilities to list here. The scanner should give you several suggestions for troubleshooting. Given that it happened after turning the wheels sharply, I would have a look at wiring.