Does a defendant who accepts a plea agreement that includes a specified sentence have an implicit waiver of his right to challenge the sentence at the Court of Appeal?

not lack fundamental jurisdiction. The rationale behind this policy is that defendants who have received the benefit of their bargain should not be allowed to trifle with the courts by attempting to better the bargain through the appellate process." (People v. Hester (2000) 22 Cal.4th 290, 295 [defendant's acceptance of a plea agreement that included a specified sentence constituted an implicit waiver of his right to claim the sentence violated section 654], citing People v. Couch (1996) 48 Cal.App.4th 1053, 1056-1057 [acceptance of specified sentence barred appellate claim of error in imposing it]; People v. Nguyen (1993) 13 Cal.App.4th 114, 122-123 [same].)