Circuit Description - DTC P3100 - Information Code 136, 137: Notes

WARNING: This page is about a different car, the 2002 Toyota Prius. However, it is still accessible from the selected car via links, so may be relevant.

NOTE:

When using an OBD II scan tool other than TOYOTA hand-held tester, check all the steps.
When using TOYOTA hand-held tester, confirm the information code and check it.

The HV ECU compares Ne signal with G signal that are sent from the ECM and checks whether the engine RPM signal is correct or not.