What is the test for rescuing a plea bargain where a defendant is charged with possession of a concealed weapon in a vehicle?

Defendant relies primarily on Ellsworth v. Superior Court (1985) 170 Cal.App.3d 967. In that case, the defendant was charged with possession of a concealed weapon in a vehicle (Pen. Code, 12025, subd. (a)) and possession of a weapon by a felon (Pen. Code, 12021). He agreed to plead guilty to the Penal Code section 12021 charge in exchange for dismissal of the Penal Code section 12025 charge. The court concluded that the People could not rescind the plea bargain in order to prosecute the defendant on the dismissed charge. The court explained that the defendant had "relied heavily" on the plea bargain, in that he had pled guilty, been sentenced, and served his sentence. (Ellsworth v. Superior Court, supra, 170 Cal.App.3d at p. 974.)