5 SYMPTOMS OF A BAD COOLANT TEMPERATURE SENSOR
purpose
The purpose of the coolant temp sensor is to read the temperature of the coolant that circulates through the engine. When the temperature changes, resistance changes. This is how the PCM (powertrain control module) calculates the temperature of the coolant.
location
The location of the ECT sensor varies between cars. Typically, it can be found near the thermostat. You can find the thermostat by locating the lower radiator hose and following it straight to the engine (as shown in the video below).
symptoms
engine light
The first symptom of a bad coolant temperature sensor is an engine light. When the engine control module senses something wrong with the sensor, it will turn on the engine light. Here are some codes related to a bad ECT sensor:
P0115
P0116
P0117
P0118
P0119
Ensure you can access your car's diagnostic codes by acquiring an OBD2 scanner here.
overheating
The second symptom you might be experiencing with your car is an overheating engine. This can be due to the cooling fans not turning on. The PCM commands the radiator fans to turn on as soon as the engine reaches 200°F. If the sensor is faulty and tells the PCM it’s reading 120°F, it’s never going to be able to turn on the fans, resulting in your engine overheating.
poor mpg
The third symptom of a faulty coolant temperature sensor is poor gas mileage. The sensor could be sending a faulty reading of a colder engine than what it actually is. When the PCM reads a colder engine, it wants to add more fuel. This happens because the PCM always wants to have the perfect air-fuel ratio, which is14.7 air to 1 gasoline. When the engine is cold, the air is more dense, so there’s more of it. When there’s more air, there should be more fuel. This is why a faulty reading from the sensor can make the engine use more fuel than it should, resulting in poor gas mileage.
black smoke
The fourth symptom you could be experiencing is black smoke coming out of the tailpipe. This can happen If the sensor is giving a bad reading where the PCM commands more fuel than whats needed. The unburnt fuel gets kicked to the hot tailpipe, where it burns and turns into a black smoke.
Reduced power
The fifth symptom of a bad coolant temperature sensor is reduced engine power. The sensor is a contributor to running the perfect air-fuel ratio for combustion, and if it’s faulty it’s going to throw these numbers off. This Causes an inefficient burn, which leads to lower engine performance.
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