Check this link. It may answer your question.
https://dot.ca.gov/programs/traffic-operations/cvef/weigh-stations
CARGO VAN -- It depends on the load and the use. Technically, they are a motor truck according to CVC Section 410 and, therefore, required to stop at the weigh stations.
Discussion: Yes, technically a cargo van is a motor truck according to CVC Section 410 and, therefore, required to stop at the scales.