Engine Coolant Temperature Sensor 1 Circuit Range/Performance
The P0116 code means the vehicle's onboard diagnostic system has detected: Engine Coolant Temperature Sensor 1 Circuit Range/Performance. This is a moderate severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- easy
- Estimated cost
- $15-$60 for thermostat or sensor
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Common Symptoms
- Check Engine Light on
- Heater may not produce hot air
- Temperature gauge reads low
- Extended warm-up time
- Poor cold-start fuel economy
Probable Causes (Ranked by Likelihood)
- Thermostat stuck open (engine never reaches operating temperature) Very High
- Partially failed ECT sensor giving slow or low readings High
- Air pocket in cooling system near sensor Moderate
- Incorrect thermostat temperature rating Moderate
Step-by-Step Diagnostic Procedure
-
Monitor ECT reading during warm-up. It should reach operating temperature (typically 195-210F) within 5-7 minutes of driving.
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If temperature plateaus at 150-160F, the thermostat is likely stuck open. Replace it.
-
Compare ECT reading to an infrared thermometer on the coolant hose near the sensor.
-
Check for air in the cooling system by feeling for air bubbles at the sensor location.
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Replace ECT sensor if thermostat checks out normal.
Common Fixes by Vehicle
What techs usually find when diagnosing P0116 on specific vehicles — tap your vehicle for the fix and the exact part:
2005-2015 Toyota Camry/Tacoma/Tundra 2.7L/4.0L/4.6L Moderate DIY
ECT performance fault — most often a stuck-open thermostat preventing the engine from reaching proper operating temp. Replace the OEM Toyota thermostat (don't use cheap aftermarket — fail rate is very high). Bleed the cooling system through the bleeder screw on the water inlet.
Labor: 1-2 hr2005-2014 GM 5.3L/6.0L/2.4L (Silverado, Equinox, Malibu) Easy DIY
ECT sensor performance/rationality fault. Replace the ECT sensor on the cylinder head — a simple $15 fix. If coolant shows rust, flush the system with dexcool-compatible coolant. A stuck-open thermostat is the second most likely cause.
Labor: 30-45 min2008-2015 Honda Accord/Pilot 3.5L J35 Moderate DIY
ECT performance issues often point to the 2-pin ECT sensor on the back of the engine block. Replace with Honda OEM. Also verify the thermostat housing isn't cracked (very common Honda failure at 100K+).
Labor: 45-60 minFrequently Asked Questions
How do I know if it is the thermostat or the ECT sensor causing P0116?
Compare the scan tool ECT reading to an infrared thermometer on the coolant hose. If the scan tool reads much lower than the actual hose temperature, the sensor is at fault. If both read low after full warm-up, the thermostat is stuck open.
Sources
This page is built from documented references. Verify against your own service info before repair work.
P0116 on Diesel, EV & Equipment
The same code ID appears across other engines and platforms. The diagnostic flow varies by manufacturer — these are the platform-specific breakdowns:
See All Codes & Fixes for Your Vehicle
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