1) Disconnect the power supply CM connector (B420).
2) Check continuity between the power supply CM connector and the push button ignition switch connector using a tester.
Connector & terminal
(B420) No. 14 — (B423) No. 7: (B420) No. 37 — (B423) No. 2:
Is there continuity?
Repair or replace the open circuit of harness.