Cal. Commercial Code § 10517

(a) A lessee may revoke acceptance of a lot or commercial unit whose nonconformity substantially impairs its value to the lessee if the lessee has accepted it: (1) Except in the case of a finance lease, on the reasonable assumption that its nonconformity would be cured and it has not been seasonably cured; or (2) Without discovery of the nonconformity if the lessee’s acceptance was reasonably induced either by the lessor’s assurances or, except in the case of a finance lease, by the difficulty of discovery before acceptance. (b) A lessee may revoke acceptance of a lot or commercial unit if the lessor defaults under the lease contract and the default substantially impairs the value of that lot or commercial unit to the lessee. (c) If the lease agreement so provides, the lessee may revoke acceptance of a lot or commercial unit because of other defaults by the lessor. (d) Revocation of acceptance must occur within a reasonable time after the lessee discovers or should have discovered the ground for it and before any substantial change in condition of the goods which is not caused by the nonconformity. Revocation is not effective until the lessee notifies the lessor. (e) A lessee who so revokes has the same rights and duties with regard to the goods involved as if the lessee had rejected them.