Engine Coolant Temperature Sensor Circuit High
Indicates a high voltage reading from the engine coolant temperature sensor.
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What it means (plain English)
The engine coolant temperature sensor (ECT) is telling the computer that the coolant temperature is higher than normal, usually over 250°F (121°C). This can happen if the sensor is faulty or if there's a real problem with overheating.
What the computer is actually seeing
The ECU monitors the ECT sensor's voltage, which should be between 0.5V to 4.5V depending on coolant temperature. When the voltage exceeds 4.5V, it's interpreted as a fault.
What a healthy reading looks like
Expected voltage values from the ECT sensor should be within 0.5V to 4.5V under normal operating conditions; higher than this may trigger code SPN 0606.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 1Confirm the code with a scan tool; if present, proceed to the next step.
- 2Inspect the ECT sensor wiring and connector for corrosion or damage. Repair or replace as necessary.
- 3Check the coolant level; ensure it’s not low, which could affect temperature readings.
- 4Measure the voltage at the ECT sensor connector with the engine running; it should be between 0.5V and 4.5V. If it's above 4.5V, replace the sensor. If normal, check for current draw issues.
- 5If the sensor and wiring are okay, check for overheating issues in the engine. Use an infrared thermometer to compare the sensor reading with actual coolant temperature.
Common causes
- Faulty engine coolant temperature sensor
- Wiring issues (open short or corrosion)
- Coolant leaks causing inaccurate readings
- Issues with power supply to the sensor
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's not recommended to drive, as the engine could overheat, leading to serious damage.
Will this code come back after clearing?
If the issue isn't fixed, yes, the code is likely to return.
Why does this issue sometimes pair with overheating?
Because a failing ECT sensor can give false high readings, leading the computer to think there's an issue, or it can indicate real overheating due to engine problems.
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