Engine Coolant Temperature Sensor Circuit Range/Performance
The P0116 code indicates that the Engine Control Module (ECM) has detected a problem with the Engine Coolant Temperature (ECT) sensor circuit's range or performance. This typically means the sensor's output voltage is outside the expected range or the sensor is responding too slowly to changes in coolant temperature. The ECT sensor is a thermistor that changes resistance with temperature, and the ECM monitors its signal to adjust fuel injection, ignition timing, and cooling fan operation. A faulty sensor, wiring issues, or a stuck thermostat can cause this code.
01. Most Common Causes
- Faulty engine coolant temperature sensor
- Open or shorted wiring in the ECT sensor circuit
- Poor electrical connection at the sensor or ECM
- Stuck open or closed thermostat
- Low coolant level or air in the cooling system
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Poor fuel economy
- Engine running rich or lean
- Hard starting, especially when cold
- Overheating or slow warm-up
03. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Visually inspect the ECT sensor connector and wiring for damage or corrosion.
Step 3: Check coolant level and condition; verify thermostat operation.
Step 4: Measure ECT sensor resistance at known temperatures (e.g., 2000-3000 ohms cold, 200-300 ohms hot).
Step 5: Compare sensor readings with a scan tool to actual coolant temperature using an infrared thermometer.
Step 6: Test the sensor signal wire for voltage (typically 5V reference) and ground continuity.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances. The ECM may use a default temperature value, causing poor performance, reduced fuel economy, and potential engine damage if overheating occurs.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150, including parts (ECT sensor $20-$50) and labor (0.5-1 hour). Additional costs may apply if wiring repairs or thermostat replacement is needed.