An insulation tester is absolutely necessary in order to be able to make sure the hybrid vehicle does not have internal shorts in the HV battery or transmission setting a DTC. Check out the Electronic Specialties 550 at vehicleservicepros.com/10895086.
Electronic Specialties' Insulation Tester, No. 550, can supply 250, 500 and 1000V test voltages for complete insulation testing on Hybrid-electric vehicles. It has a large dual display with white LED backlighting and a test-hold function for easy operation. Includes six AA batteries, test leads and blow mold case.