I found 2 different amounts by searching for CARPOOL VIOLATION CALIFORNIA:
17. What if I used a HOV/carpool-lane by mistake?
Vehicles that do not meet the requirements for high-occupancy-vehicle (HOV)/carpool-lane use are subject to a California Highway Patrol (CHP) citation with a minimum fine of $341.
Courts will be able to allow those suffering financial hardship to pay off fines for traffic infractions through community service. Under Penal Code section 1209.5, the court will decide what constitutes a financial hardship. Over the years, traffic tickets have gotten increasingly more expensive. A carpool violation, for example, is $271, and running a red light is also $271.
<in my best E.T. voice> ooouch!
I guess 35 doesn't sound so bad after all
Isn't there a phone number to call for info on the ticket?