Yes. A faulty coolant temperature sensor can contribute to a misfire by confusing the engine control module about engine temperature, which alters fueling and ignition timing. However, most misfires are caused by ignition components, fuel delivery issues, or mechanical problems, and the CTS is typically a contributing factor rather than the sole cause.
How a CTS affects engine management
The coolant temperature sensor provides the engine control module (ECM) with real-time data about engine temperature. When the engine is cold, the ECM enriches the fuel mixture and may adjust idle to help start and warm up. As the engine reaches operating temperature, fueling is adjusted leaner and idle is stabilized. If the CTS is out of spec—stuck cold, stuck hot, or reporting erratic values—the ECM can run the wrong fuel map, leading to rough running, stalling, or, in some cases, misfires.
Direct vs. indirect impact on combustion
Direct ignition misfires are usually caused by spark plugs, ignition coils, or wiring. A faulty CTS does not fire a cylinder, but it can indirectly trigger a misfire by producing an imbalanced air-fuel mixture or inconsistent ignition timing due to incorrect fuel trims.
Codes you might see
CTS faults commonly trigger coolant-temperature codes and can appear alongside misfire codes if the mixture becomes unstable. Look for P-code readings such as P0115 (engine coolant temperature circuit malfunction) or P0118 (CTS sensor high input), as well as generic misfire codes like P0300-P0306 when the condition affects combustion.
Symptoms that CTS involvement may be suspected
The following signs may indicate a coolant sensor problem impacting fueling and potentially contributing to misfires.
- Rough idle or stalling, especially when starting from cold
- Hard starting or extended cranking at cold temps
- Fluctuating fuel trims on a scan tool (long-term or short-term trims shifting unexpectedly)
- Degraded fuel economy and irregular engine performance
- Check Engine Light with coolant-temperature related codes (P0115-P0118) and possibly misfire codes (P0300-P0306)
Because many issues share similar symptoms, a proper diagnostic is essential to confirm CTS involvement.
How to diagnose CTS involvement and distinguish it from other causes
To determine if the CTS is driving misfire risk, technicians perform a structured diagnostic process that includes data review, resistance testing, and wiring inspection.
- Retrieve live data and confirm the CTS reading correlates with engine temperature across operating ranges
- Compare CTS readings to actual engine temperature using a reliable thermometer or infrared scan tool
- Check the CTS resistance specifications for cold and hot temperatures per the service manual and measure continuity from connector to sensor
- Inspect wiring and connectors for damage, corrosion, or loose grounds; look for shorts or opens in the signal circuit
- Clear codes, drive under various conditions, and observe fuel trims and misfire data to see if a CTS fault reappears
If the CTS is found out of spec, replacement is typically recommended. After replacement, reset adaptives, perform a test drive, and recheck data to ensure fuel trims stabilize and misfires cease.
What to do if you suspect a CTS fault
Start with inexpensive checks before replacing parts. Check the engine coolant level and condition, scan for related codes, and inspect visible wiring. If you have the tools, perform a resistance check on the CTS and monitor live data. If in doubt, consult a professional technician who can perform a controlled test drive and, if needed, replacement under warranty.
Summary
A coolant temperature sensor can contribute to misfires by sending inaccurate temperature data to the engine computer, which disrupts fueling and idle control. It is usually a contributing factor rather than the sole cause, and misfires are more commonly tied to ignition or fuel-delivery problems. A structured diagnostic approach—checking codes, data, sensor resistance, and wiring—helps determine whether the CTS is at fault and whether replacement will restore smooth operation.