Counterfeit ELM327 chips (common in cheap PL2303 USB adapters) often report bad/zero voltage even when the OBD connection is working. python-obd's check_voltage=True default rejects these. Add OBD_SKIP_VOLTAGE_CHECK=1 env var to pass check_voltage=False to obd.OBD(), documented in yaris-obd.service. Also document Phase 24.6 Yaris 2013 compatibility analysis in PLAN.md. Co-authored-by: Copilot <[email protected]>