P0117 – Engine Coolant Temperature Circuit Low Input
Description
The ECM detects an abnormally low signal from the engine coolant temperature sensor, often caused by a short to ground or sensor failure.
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Compare Diagnostic ScannersSymptoms
- Check engine light on
- Poor fuel economy
- Hard starting when cold
- Rich running condition
- Cooling fans running constantly
Causes
- Short to ground in ECT wiring
- Faulty ECT sensor
- Corroded connector
- ECM fault
- Low coolant level
Diagnosis
- Scan ECT data
- Inspect wiring
- Check coolant level
- Compare sensor reading to actual temp
- Test sensor resistance
Repair
- Repair wiring
- Replace ECT sensor
- Fix connector
- Correct coolant level
- Replace ECM if needed
