many people ask such questions on this site, and there can never be a direct answer as sentencing depends on too many factors. the best person to ask such a question of would be the attorney representing him on his case.
Vehicle Theft, Penal Code 10851, is a "wobbler," meaning it can be charged as a felony with a maximum prison sentence of three years, or as a misdemeanor with a maximum of a year in jail.
There is no way to know what your cousin's sentence might be. It depends on the circumstances of the case, his past criminal record, his age and a number of other factors. His lawyer is in a much better position to answer your question.
Please understand that this is a general discussion of legal principles by a California lawyer and does not create an attorney/client relationship. It's impossible to give detailed, accurate advice based on a few sentences on a website (and you shouldn't provide too much specific information about your legal matter on a public forum like this, anyway). You should always seek advice from an attorney licensed in your jurisdiction who can give you an informed opinion after reviewing all of the relevant information.
As Mr. Kaman knows, there are laws of the Universe in addition to the Penal Code and Vehicle Code. One of them is that any correction of another person's typo on the Internet will invariably include another typo.
I actually combined two sections. Auto theft can be charged as either Vehicle Code 10851 or Penal Code 487(d)(1). The punishment is the same for either offense.
It is interesting to note that this case occurred in 2007. If the DA did not file the case until recently, your friend may have lost out on key evidence that may have been available had the charges been filed earlier. This could be a plausible defense to raise. Additionally, your friend could be charged with a theft related offense (10851 or 487 as explained by previous attorneys below) or receiving stolen property under Penal Code 496 -- all of these charges may be filed as misdemeanors or felonies. In any event, if the case is filed as a misdemeanor, your friend may be able to receive little to no jail time with probation if there are no priors in his or her past. If priors do exist, look at more jail time with the possibility that a felony may be filed.
If he/she has a reputable attorney who can talk to the DDA handling the case, the case could possibly be negotiated for straight probation with restitution, or perhaps a civil compromise (if filed as a misdemeanor). Your friend should really seek guidance from an attorney to get the best deal. Best of luck!