Error Code P0116 Causes, Symptoms, and Fixes

• Illuminated Check Engine Light (MIL) .
• Poor fuel economy due to incorrect fuel mixture .
• Engine overheating or inaccurate temperature gauge readings .
• Hard starting, particularly when the engine is cold .
• Rough idling, engine hesitation, or stalling .
• Black or dark exhaust smoke from an overly rich fuel mixture .
• Engine may run fine once fully warmed up, with symptoms most noticeable during warm-up .

1. Faulty Engine Coolant Temperature (ECT) Sensor: The sensor itself can fail internally, providing a static, skewed, or out-of-range signal .
2. Wiring or Connector Issues: Damaged, frayed, corroded, or loose wires and connectors in the ECT sensor circuit can cause high resistance, shorts, or open circuits .
3. Low Engine Coolant or Coolant Leaks: Insufficient coolant around the sensor can cause it to read inaccurately .
4. Faulty Thermostat: A thermostat stuck open can prevent the engine from reaching normal operating temperature, causing a rationality fault when compared to other sensors .
5. Faulty Intake Air Temperature (IAT) Sensor: Since the ECM compares ECT and IAT readings, a faulty IAT sensor can cause a false P0116 code .
6. Faulty Engine Control Module (ECM/PCM): In rare cases, the computer itself may have an internal fault .

1. Connect an OBD2 scanner​ to read and confirm code P0116. Check for any related codes (e.g., P0115, P0117, P0118) and review freeze frame data to see the conditions when the code set .
2. Perform a visual inspection of the ECT sensor and its wiring harness. Look for corrosion, damage, or coolant leaks at the sensor .
3. Check the engine coolant level and condition. Top up or flush the coolant if necessary .
4. With the engine cold and key on, use a car code reader​ capable of displaying live data to monitor the ECT sensor reading. It should closely match the ambient temperature. Start the engine and watch the temperature rise steadily to the thermostat opening point (typically around 195°F / 90°C) .
5. Use a digital multimeter to test the sensor’s resistance. Compare the ohms reading at a specific coolant temperature to the manufacturer’s specifications. A common test is to check resistance when cold and when hot .
6. Test the sensor’s wiring circuit for the correct 5-volt reference signal, a good ground, and continuity in the signal wire back to the ECM .

• Top Up Coolant: If low, refill the cooling system with the correct type of coolant and bleed any air pockets .
• Clean Connectors: Disconnect the ECT sensor connector, clean any corrosion with electrical contact cleaner, and reconnect securely .
• Repair Wiring: Repair any damaged wires with solder and heat shrink tubing. Replace corroded connectors .
• After repairs, clear the codes with your obd code reader​ and perform a test drive to see if the code returns.

• Replace the ECT Sensor: If testing confirms a faulty sensor, replace it. Be sure to refill coolant as needed and bleed the cooling system .
• Replace the Thermostat: If diagnostics point to a stuck-open thermostat, replace it and the coolant .
• Replace the IAT Sensor: If the IAT sensor is found to be faulty, replace it .
• In the rare event of a faulty ECM, professional reprogramming or replacement is required .

• Toyota/Lexus (e.g., Corolla, Camry, Sienna): Prone to P0116 from failing ECT sensors and wiring connector issues. The sensor is often located near the thermostat housing .
• Honda/Acura (e.g., Accord, Civic, CR-V): Common causes include faulty ECT sensors and cooling system issues. Live data monitoring is key for diagnosis .
• Ford (e.g., Fusion, F-150, Escape): Frequently experiences P0116 due to ECT sensor failures, particularly in models like the 2010-2016 Fusion .
• General Motors (Chevrolet, GMC, Buick, Cadillac): GM vehicles have specific diagnostic logic comparing ECT and IAT sensors after a long ignition-off period. Wiring issues and sensor failures are common .
• Chrysler/Dodge/Jeep: Similar to GM, these vehicles use rationality checks between sensors. Faulty sensors and corroded connectors are typical culprits .
• Nissan/Infiniti: ECT sensor failures and related wiring problems can trigger P0116.
• Hyundai/Kia: Commonly sets P0116 due to failing ECT sensors or low coolant levels.
• BMW: The ECT sensor is critical for engine management. Failures can lead to poor performance and overheating.

• Mercedes-Benz: Sensitive to accurate temperature readings. Faults often stem from the sensor itself or wiring harness issues.
• Subaru: ECT sensor failures are common and can cause significant drivability issues.
• Volkswagen/Audi: Prone to electrical gremlins; P0116 often points to wiring faults or a failing sensor.

P0116 Frequently Asked Questions

• What is the first thing I should check when I get a P0116 code?

  First, use an obd2 code scanner​ to confirm the code and check freeze frame data. Then, visually inspect the ECT sensor and its wiring connector for obvious damage or coolant leaks .

• Can I drive my car with a P0116 code?

  You may drive for a short time, but it is not recommended . The engine may run poorly, overheat, or suffer from reduced fuel economy. Driving for extended periods can potentially cause engine damage .

• Is a P0116 code serious?

  It is considered a moderate to serious code . While the car may still run, incorrect temperature data can lead to poor performance, increased emissions, overheating, and long-term engine damage.

• How much does it cost to fix a P0116 code?

  Repair costs typically range from $100to$300 USD. The ECT sensor itself usually costs between $20and$100. Labor adds $80to$200, depending on the vehicle and shop rates.

• Can a bad thermostat cause a P0116 code?

  Yes, a thermostat stuck open can prevent the engine from warming up properly. The ECM expects to see a certain rate of temperature increase; if it doesn’t happen, it can set a P0116 code .

• Can I test an ECT sensor with a multimeter?

  Yes. Measure its resistance (ohms) when the engine is cold and compare it to the resistance when the engine is hot. The resistance should drop significantly as temperature increases. Refer to a vehicle-specific resistance chart .

• Will disconnecting the battery clear a P0116 code?

  It may clear the code temporarily, but it will return once the ECM completes its monitoring cycle if the underlying problem is not fixed .

• My car has P0116 and is overheating. Could it be something else?

  Yes. While P0116 points to a sensor circuit issue, the overheating itself could be caused by a separate problem like a clogged radiator, failed water pump, or a blown head gasket. The faulty sensor might just be reporting the overheating accurately.

• How do I know if it’s the sensor or the wiring?

  Use a multimeter to check for 5 volts at the sensor connector (key on, engine off). If voltage is present, unplug the sensor and measure its resistance. If the resistance is within spec for its temperature, the wiring or ECM is likely at fault. If no voltage is present at the connector, there is a wiring or ECM problem .

• What tools do I need to diagnose P0116 myself?

  You will need an OBD2 scanner​ or a dedicated car code reader​ capable of reading live data, a digital multimeter, basic hand tools, and possibly a infrared thermometer to verify actual coolant temperature .

Related OBD2 Fault Codes

• P0115: Engine Coolant Temperature (ECT) Sensor Circuit Malfunction.
• P0117: Engine Coolant Temperature (ECT) Sensor Circuit Low Input.
• P0118: Engine Coolant Temperature (ECT) Sensor Circuit High Input .
• P0125: Insufficient Coolant Temperature for Closed Loop Fuel Control – Often related to a thermostat stuck open .
• P0128: Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature) .