What does the engine cooler temperature (ECT-) sensor do? What happens when the water temperature sensor malfunctions? What are the symptoms for a coolant sensor malfunction? How to replace the temperature sensors ?….
The engine coolant temp (ECT) sensor monitors the engine’s internal temperature. It is a very simple sensor. It is used for measuring the coolant temperature inside the engine block. The sensor detects temperature variations and transmits to the Engine Control Units (PCM), a signal indicating that the engine water has become extremely hot, cold or normal.
This sensor is vital for the smooth operation of engine management. A disruption in the coolant temperature sensor will have an impact on the entire engine’s operation strategy. The coolant temperature sensor is commonly referred to as the “master sensor”.
Operating temperature affects many parts of the PCM, including fuel, ignition and emissions. The engine’s operating temperature affects the starting strategy. It will develop a different strategy for hot engines and one for cold ones. This optimizes engine performance and idling quality as well as emission values. It can also cause many problems if the coolant sensor malfunctions or sends an incorrect value to PCM.
How does the coolant temperature sensor affect engine operation?
The PCM can use data from the coolant sensor for any or all the following control functions.
The PCM keeps the injectors open when the engine is cold. This improves the engine’s idling and prevents problems such as misfire or stalling that a cold engine might experience when it warms up. The engine reaches normal operating temperature and adjusts the injector timing to reduce fuel consumption and emissions. If the sensor reads cold, the engine will start to burn more fuel and produce excessive exhaust gas. The vehicle will stall, misfire, and idle indefinitely if the sensor is hot. It can also directly impact the operating conditions of the cold engine.
– Increases or decreases the ignition timing of sparkplugs. The engine temperature affects the ignition advance. This can also impact engine performance, fuel economy, and other aspects.
– The PCM won’t allow the EGR valve open until the engine is warm. If the EGR valve is opened while the engine remains cold, it can cause stalling of misfire at idle.
Until the engine heats up, fuel vapors in the EVAP container are not to be removed.
– The PCM might ignore the rich/lean signal from the oxygen sensor until engine coolant reaches a specific temperature. The PCM cannot adjust the mixture of fuel and air, which can cause excessive fuel consumption, engine contamination, and many other problems. The spark plugs also become dirty.
– The PCM might not lock the torque converter until the engine heats up. This will improve the performance of cold engines.
– The coolant temperature sensor signals the PCM to turn the cooling fan on or off. It is vital to turn on the fan in order to avoid the engine overheating. Some vehicles might have a separate fan switch or sensor for cooling fan circuit.
Different types of coolant temperature sensors
Coolant sensors are often “thermistors”, which have a resistance that changes with temperature. The majority of coolant sensors are “NTC” (Negative Temperature Coefficient), where the resistance decreases as the temperature increases. This type of sensor has a high resistance when the engine is cold. The internal resistance of the sensor drops to its lowest value as the engine heats up and reaches normal operating temperatures.
A typical GM cooler sensor can resist temperatures of 10,000 ohms at 32°F, but it may drop to below 200 ohms if heated (200°). A Ford coolant sensor could read 95,000 Ohms at 32°F and drop down to 2,300 Ohms at 200°F.
The resistor characteristics of different products will differ depending on the model and type. Replace any sensor that is not reading within the range.
The two wires of a coolant sensor are the input and return. The PCM sends a 5 volt reference voltage signal to the sensor. The sensor’s resistance is then sent back to the computer. Based on the voltage of the return signal, the PCM calculates coolant water temperature.
Two-stage coolant temperature sensors can be used by some vehicles to measure coolant temperature more accurately. The control unit can adjust the reference voltage value to the water temperature sensor in order to measure engine water temperature when it rises above a predetermined value.
Certain older vehicles use a different kind of coolant temperature sensors. These switches are temperature-controlled and can be opened/closed at a specific temperature. The sensor connects to a relay which turns the cooling fan on/off and sends an alert signal back to the cluster.
Locate the Coolant Temperature Sensor
It is located near the thermostat in the intake manifold. Some vehicles have it on the cylinder head. Two sensors are required for V6 and V8 engines. Some vehicles might have two sensors. One for the cooling fan and one for PCM.
The sensor’s tip is in direct contact the liquid. This is essential for precise measurement. The sensor could read incorrectly if the coolant level drops.
What Happens If the Sensor FAILS?
Many engine functions are triggered by the coolant temperature sensor. A faulty sensor or circuit can cause low engine performance and high levels of emissions. This could cause the vehicle not to pass the emissions test. The vehicle will be running with a rich mixture, which means that fuel consumption is higher. You may experience major problems like idle fluctuation, misfires and stalling.
The sensor may fail, and the cooling fan won’t turn on. This could cause the engine overheat.
Many sensor problems are caused when wiring is defective, worn or damaged connectors.
P0115 …. ECT Circuit Malfunction
P0116….ECT Circuit Range/Performance Problem
P0117 ….ECT Low Input
P0118 ….ECT Circuit High Input
P0119 …. ECT Circuit Intervals
Troubleshooting Coolant Temperature Sensor
You should inspect the sensor visually. The sensor should be visually inspected for cracks or fluid leakage. You can test the resistance and voltage readings to determine if the sensor works.
The data can be viewed using a scan tool connected directly to the sensor. The engine should have a sensor value of approximately 200 degrees in warm and low temperatures. Defective sensors must be replaced if they read incorrectly or do not change. Also, the wiring system must be checked.
You can also check the values and compare their properties with an ohmmeter, digital voltmeter, or both. The sensor should be replaced if it is damaged, shorted or reading out of range.
If the coolant sensor’s resistance is within the specification and changes with engine temperature, it is likely that the wiring or PCM is defective. Before any parts can be replaced, further diagnosis is required.
You can check the harness by sending a signal with the sensor simulator tool to the PCM. If the wiring is good, then the problem is with the PCM.
Voltage Controls for Coolant Temperature Sensors
To check the output of the sensor, you can use a digital storage oscilloscope or voltmeter. The sensor should produce around 3 volts of voltage, but its characteristics may vary. As the engine heats up, and the engine reaches operating temperature the voltage should drop to around 1.2 to 0.5%.
The sensor is defective when the voltage value measured by a voltmeter at the output of the sensor shows 5 volts.
How to replace a coolant temperature sensor
The water temperature sensor should only be replaced if it is failing. Experts recommend replacing the sensor with the engine overhaul. Over time, the sensor could become damaged or read incorrectly. Many potential problems can be solved by replacing the sensor. To ensure that the engine management system functions properly, a sensor must be replaced if it is not reading correctly.
It’s a good idea for the engine to be replaced with the coolant sensor or thermostat if it has been subjected to severe overheating. Extreme heat can damage these components and cause them to fail or malfunction quickly.
To replace the sensor, you must drain the coolant. It doesn’t necessarily have to drain all of the radiator. Open the drain valve, and drain the coolant until it is below the sensor. Remove the old sensor carefully and replace it with a new one. You must ensure that all air is removed from the system. An engine that is too hot can lead to a false reading.
