P0666
Control Module Internal Temperature Sensor A Circuit
What it means
P0666 means Control Module Internal Temperature Sensor A Circuit.
Where it lives
For P0666, the circuit described runs through the sensor. The description of P0666 reports a fault at the sensor.
Check these first
- An open or short in the internal temperature sensor circuit
- A failed internal temperature sensor
- A poor module ground
- A module running hot from a nearby heat source
- A failed control module
What to do next
- Read the internal temperature on a scan tool
- Check the module ground and power feed
- Look for a heat source near the module
- Test the sensor circuit for an open or short
- Replace the control module if the sensor circuit will not read
- Clear the code and retest
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Updated
Generic SAE J2012 definition. Last updated 2026-10-10.