unknown code p121?

[KParsons]

i have had the abs light on for some time. checked the codes p121 came up. did a search no listing. the truck runs fine, 2006 auto. any idea,s kp

 

[JordanB]

I'm not sure what a p121 code means but my rear wheel speed sensor was bad when my ABS light came on. Went off once and then came back on a couple of months later and didn't go off until the dealer fixed it. They said it was fairly common on these trucks. Hope this helps! : )