I have a 05 h2 with the brake, ABS, and T/C lights on the dash. pulled the codes and have c0121 which is valve relay circuit malfunction. doing a search can't find much info on this codes is this Relay in the EBCM and require replacement of the EBCM or is it located elsewhere on the truck?

 

Hey Poboy....I had that issue a few weeks ago...they had to replace my speed wheel sensor. About $100.00 bucks and about 30mins....hope this helped