Common Symptoms
- Check Engine Light illuminated
- Engine runs rich or poor fuel economy
- Hard starting when cold
- Cooling fans run continuously at high speed
- Engine may run in open loop mode constantly
- Black smoke from exhaust on cold start
Most Likely Root Causes
- Faulty engine coolant temperature sensor
- Shorted wiring or connector at ECT sensor
- Corroded or damaged ECT sensor connector terminals
- Short to ground in ECT sensor circuit wiring
- Failed engine control module
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Component Location
The engine coolant temperature sensor is typically located in the engine block, cylinder head, or upper radiator hose near the thermostat housing.
Manufacturer Notes
Some manufacturers use different ECT sensor specifications and may require model-specific testing procedures for accurate diagnosis.
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