P0116 — Engine Coolant Temperature Sensor Range/Performance

P0116 means the coolant temperature reading is out of the expected range for the engine's operating conditions. A stuck thermostat or a lazy sensor are the usual suspects.

Cost range: $50–$450. Severity: medium. Safe to drive? Yes, but verify the engine isn't actually overheating before dismissing it.

Most common causes of P0116

1. Stuck-open thermostat — Engine never reaches full temperature — check with an infrared thermometer. ($150–$400)
2. Failed coolant temperature sensor — Inexpensive part, easy swap on most engines. ($50–$200)
3. Low coolant level — The sensor reads air instead of coolant. ($20–$150)
4. Air pocket in the cooling system — Bleed the system properly after any coolant work. ($50–$150)

Symptoms drivers report with P0116

• Heater blows cool
• Poor fuel economy
• Temperature gauge reads low
• Cooling fan runs constantly