Question

2004 Chevrolet Silverado with engine code P0021. What does this code mean?

Answer 1

You must replace the Camshaft Position Actuator Solenoid Valve to fix the problem.

P0021 Chevrolet Code - Intake Camshaft Position System Performance Bank 2
Read more: https://www.autocodes.com/p0021_chevrolet.html

Answer 2

what model Silverado do you have? and what engine size?

I only up Silverado 1500 all the engine size and Chevy does not use P0021

try to use a different OBD-II reader the one you are using may not be compatible with your car