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P0115 P0xxx · パワートレーン (P) 重大度中
Engine Coolant Temperature Circuit Malfunction
The ECT signal is out of range or implausible. The ECU then cannot judge warm-up state, so fuelling, fan control and transmission behaviour all go wrong.
重大度の目安： 中 — 走行性または排出ガスに影響。今週中に点検を予約してください
確認できる症状
- Hard cold start
- Cooling fans running constantly or never
- Rich running
- Temperature gauge dead or pegged
主な原因
可能性の高い順に並んでいます。上から順に確認してください。
- 1 Failed coolant temperature sensor
- 2 Open or shorted wiring
- 3 Low coolant level causing the sensor to read air
- 4 Corroded connector
点検・修理の手順
費用が安く侵襲の小さい項目から — これらのコードの大半は部品の問題ではありません。
- ✓ Compare ECT with intake air temperature after a cold soak — they should be within a few degrees.
- ✓ Check the coolant level before blaming the sensor.
- ✓ Measure sensor resistance across the pins and compare with the temperature/resistance table.
- ✓ Inspect the connector for coolant ingress (a known issue on several brands).
修理の選択肢
- Replace the coolant temperature sensor
- Repair the wiring
- Top up and pressure-test the cooling system
P0115 — よくあるご質問
Why does the fan run with a cold engine? +
When the ECU loses the ECT signal it drives the fan as a protective default.
Can low coolant trigger this code? +
Yes — a sensor sitting in an air pocket reads nonsense.