7 Symptoms of a Bad Coolant Temp Sensor
Today’s vehicles rely on complex network of sensors which monitor engine efficiency. But when just one sensor fails, an array of concerning symptoms can emerge.
The engine coolant temperature sensor is especially vulnerable. Its failure can lead to severe issues. Let’s look at the common symptoms of a faulty coolant temp sensor, why it fails, and its typical replacement cost.
Bad Coolant Temperature Sensor Symptoms
With time, coolant temperature sensors in many vehicles have a tendency to fail. In most cases, this comes as a result of continuity loss within the sensor itself.
When this occurs, a false temperature value is sent to the vehicle’s ECM, which leads to improper system response. As a result several symptoms often present themselves in short order. The following are 7 of the most common symptoms associated with a failing engine coolant temp sensor.
#1 – Check Engine Light
One of the most common symptoms associated with engine coolant temperature sensor failure is the sudden appearance of a check engine light. By its nature, a vehicle’s on-board diagnostics system stores trouble codes associated with many component failures and electrical circuit related problems.
#2 – Poor Fuel Economy
Another symptom commonly associated with the failure of a coolant temperature sensor is poor fuel economy.
This stems from the fact that coolant temperature sensor feedback plays a vital role in the calculation of fuel delivery and timing. More often than not, a faulty engine coolant temperature sensor will incorrectly reflect a cool temperature reading.
#3 – Dark Colored Exhaust
As previously mentioned, a faulty coolant temperature sensor that has defaulted to a permanently cold reading will typically cause an engine to over-fuel (aka: run rich). In severe cases, this smoke can become very dense, and quite noticeable to anyone nearby.
#4 – Engine Overheating
One of the most severe symptoms of coolant temperature sensor failure is engine overheating. While some vehicles utilize an auxiliary temperature sensor to regulate fan operation, the vast majority of makes and models rely upon the engine coolant temperature sensor to sustain this function.
If an engine coolant temperature sensor of this type fails, it is common for the vehicle’s radiator fan to be inoperable. As a result, engine temperatures begin to spike, risking damage to other components.
#5 – Fluctuating Temperature Gauge
If the coolant temp sensor isn’t working correctly, it can provide inaccurate readings, affecting your temperature gauge and making it fluctuate. This might lead you to think your engine is overheating when it’s not, or vice versa.
Stay aware, as these wrong readings can cause unnecessary panic or even lead to potential engine damage if an actual overheating issue goes unnoticed.
#6 – Rough Idling
Due to incorrect temperature readings, your vehicle’s computer may adjust the air-fuel mixture improperly, causing an uneven and rough idle. It’s essential to keep an eye on this, as it could make your driving experience less comfortable and may lead to more significant issues.
#7 – Hard Start at Certain Temperatures
Though not as common as other symptoms, a hard start condition is occasionally presented by a faulty coolant temperature sensor. In most cases, this condition will present itself only when a vehicle’s engine is at one particular temperature, whether hot or cold.
On most occasions, this is the result of a sensor which is providing a continually hot reading, even when an engine is actually cool. As a result, this typically renders a lean condition, which exponentially increases crank times.
