What this code means

The PCM has detected a malfunction with the engine coolant temperature sensor. The sensor reading does not correlate with expected warm-up behavior or is providing erratic data.

Symptoms

• Check Engine Light
• Incorrect temperature gauge reading
• Poor fuel economy
• Fan may run continuously or not at all
• Hard cold starts

Common causes

• Faulty ECT sensor
• Corroded ECT sensor connector
• Wiring issue in ECT circuit
• Low coolant level exposing sensor
• Thermostat stuck open affecting readings

Diagnostic steps

1. Compare ECT reading on scan tool with infrared thermometer measurement
2. Test ECT sensor resistance at various temperatures
3. Inspect ECT connector for corrosion
4. Check coolant level
5. Inspect wiring for damage

Repair notes

Replace the ECT sensor if its resistance does not match the temperature-resistance specification chart.

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