How to detect the signal voltage of the engine coolant temperature sensor

It is best to use an oscilloscope to observe the signal voltage change of the engine coolant temperature sensor, because the multimeter can only look at the voltage at one point in time, and the oscilloscope can see the voltage change trend.

Let's take a look at how an oscilloscope connects to a coolant temperature sensor. Coolant temperature sensors are generally divided into two wires, one power cable and one ground wire. We connect one of the channels of the oscilloscope to a BNC to banana head cable.

The red banana head is attached to a barbed needle, and the black banana head is attached to a crocodile clip. The black alligator clip is grounded, and the red needle is pierced into the power cord of the coolant temperature sensor.

Start the car engine, then turn the oscilloscope time base to at least 50s, adjust the vertical gear of the oscilloscope, and make the waveform in the appropriate position in the screen. The low-pass filtering function of the oscillator is turned on, and the low-pass filter is recommended to be 30kHz. Then wait for the waveform to change.

It can be seen that the waveform signal is a slow decline and then an upward process. The engine coolant temperature sensor uses a thermistor that is sensitive to temperature changes, when the coolant temperature is low, the sensor resistance is larger, and when the coolant temperature is high, the sensor resistance will be significantly smaller. With this feature, the sensor senses changes in coolant temperature during actual use, and transmits the electrical signal to the ECU through the continuous conversion of the circuit, which then adjusts according to the input electrical signal.

As shown in the coolant sensor signal in the figure above, as the temperature slowly increases, the voltage slowly decreases, when the voltage value drops to 400mv, you can see that the cooling fan starts to work, at this time the temperature decreases again, and the voltage begins to rise again. If you make the time base a little bigger and wait a little longer, you should see a more noticeable change. The waveform can be used to analyze whether the coolant temperature sensor is working properly, whether the fan is working properly, etc.

Turn on the ignition switch, and use the voltage of the multimeter voltage to measure the signal voltage between the signal output end of the water temperature sensor THW and the tie-iron terminal E2, which should be the same as the signal voltage corresponding to the estimated engine temperature. Place the thermometer close to the water tank, and detect the signal voltage at different water temperatures after starting the engine (cold car), which should meet the specified requirements.

Hello, the reasons why the signal voltage temperature of the coolant temperature sensor on the car is too high are low coolant temperature, faulty coolant temperature sensor, open signal circuit, and short circuit of engine iron. Imitation ignites the hope that mine will help you with the chain.

Engine coolant temperature sensor.

The cause of the high voltage of the circuit: it is the failure of the rear oxygen sensor, or it can be solved by adding a resistor. With a digital multimeter.

Measure the voltage between the engine coolant temperature sensor signal circuit and the reliable ground to see if it is within a reasonable range of volts.

If the voltage is below volts, test the engine coolant to blind the temperature sensor signal circuit for excessive resistance or an open circuit.

If the voltage is higher than volts, test the signal circuit of the engine coolant temperature sensor for a short circuit to the voltage.

If the engine coolant temperature sensor signal circuit test results are normal, and the voltage is still not within the reasonable range, there is a problem with the engine control module and needs to be replaced.

Extended Materials. Cooling water.

The resistance detection of temperature sensors can be divided into two methods: vehicle detection method and single-piece inspection method.

Vehicle inspection method. The ignition switch is placed in the OFF position, and the cooling water temperature sensor wire connector is removed and a digital high impedance is used.

The multimeter measures the resistance between the THW and E2 terminals of the sensor. The value of resistance is inversely proportional to the temperature.

Single-piece inspection method. Unplug the coolant temperature sensor harness and remove the coolant temperature sensor from the engine; Place the coolant temperature sensor in the beaker.

of water, heat the water in the cup; At the same time, the multimeter is used to measure the two terminals of the water temperature sensor under different water temperature conditions.

The value of the measured Pai Wang is compared with the standard value, and if it does not meet the standard, the water temperature sensor should be replaced.

Summary. We are happy to answer for you, dear, the possible reasons for the high voltage of the coolant temperature sensor: 1. There is a problem with the circuit of the computer board; 2. The voltage of the car is 12V, so the voltage of the car is kept at 12V, and the voltage regulator of the engine is broken, the faster the engine speed, the higher the voltage; 3. The sensor itself is faulty.

What's going on with the coolant temperature sensor voltage being too high.

We are happy to answer for you, dear, the possible reasons for the high voltage of the coolant temperature sensor: 1. There is a problem with the circuit of the computer board; 2. The voltage of the car is 12V, so the voltage of the car is kept at 12V, and the voltage regulator of the engine is broken, the faster the engine speed, the higher the voltage; 3. The sensor itself is faulty.

The main working principle of the automotive engine coolant temperature sensor is based on the characteristics of the thermistor, its resistance changes with the change of temperature, and the signal voltage also changes, and the ECU controls the amount of fuel injection according to the current water temperature signal. In layman's terms, it is to provide water temperature signals for the engine ECU, which is used for starting, idling, ignition timing during normal operation, and control of fuel injection pulse width.

First of all, you need to know whether the engine water temperature sensor is analog or switching, if it is analog, you also need to know whether it is PT100 RTD type or thermistor type, and then see what power supply is used in the measurement system, generally DC24V or DC12V, the signal of the measurement sensor needs to be input power supply and then measure the current.

You don't know this question clearly, what is the high voltage of the sensor circuit? What is the voltage you send over, what should be, these have no specific values, and there is no way to help you find the specific reason!

The water temperature sensor plug is not plugged in, or the wire is broken.

Coolant. Temperature sensor, gasoline engine.

There is generally only one carburetor; There are two EFI; Diesel seems to have one. It is generally near the water outlet. One is to provide water temperature data to the ECU, and the ECU adjusts the engine operating conditions according to the water temperature.

The other is the water temperature gauge on the dashboard. The two sensor interfaces are different and cannot be shared.

Refrigerant sensor type: 1. It continuously brings out the heat by circulation 2. Automobile engine.

The temperature is 90 degrees, and the coolant is sent to the water tank, and the water tank is connected to the air, and there is a fan to accelerate the air circulation. The temperature heat is lost.

Antifreeze. It is a kind of coolant containing special additives, mainly used in liquid-cooled engine cooling system, antifreeze has excellent properties such as antifreeze in winter, boiling in summer, waterproof scale and anti-corrosion throughout the year.

The engine coolant temperature sensor is used to detect the coolant temperature and will be converted into a temperature-related voltage signal transmitted to the engine ECU, as the basis for the ECU to correct the amount of fuel injected. If the coolant temperature sensor is faulty or fails, or the connection circuit between the coolant temperature sensor and the ECU is short-circuited or broken. Or when the surface scale is serious, it will cause a large deviation in the output signal, which causes the injector to not increase or reduce the amount of fuel injection in time, and finally makes the EFI engine start difficult to fault.

Typical symptoms of coolant temperature sensor circuit failure are: Difficulty in engine starting, unstable idle operation, and insufficient power during acceleration under cold engine conditions; Under the heat-up condition, the engine is normal when starting, idling and accelerating; The engine fault indicator is always on. Here's why:

When the engine does not receive a normal signal from the coolant temperature sensor, the engine ECIJ performs a safety insurance function to maintain the engine running. In this case, the engine takes the coolant temperature substitute value (80 clc 90) stored in its memory as the coolant temperature value. Therefore, when the engine is cold, the fuel injection volume controlled by the engine lacks the increase related to the low engine temperature, so that the mixture is thinner, and the engine will have fault phenomena such as difficulty in starting;

Hello, the current number of people consulted may not reply in a timely manner, if it is a vehicle failure problem, it is recommended to use the computer to detect the specific cause of the failure, search for "car master" can consult car problems at any time, 24 hours ** answer.

Unplug the sensor harness and remove the sensor; The sensor is placed in water and heated to water, while the resistance between the two terminals of the sensor is measured at different temperatures; The measured resistance value is compared to the standard value. If it does not meet the standard, it should be replaced.

The standard value of the supply voltage of the coolant temperature sensor should be 5V, otherwise there will be a short circuit or open circuit fault in the wiring harness.

The detection procedure is as follows:

a.Turn off the ignition.

b.Unplug the 4-pin coolant temperature sensor.

c.Hit the stupid fiber and turn on the ignition.

d.with a multimeter.

Measure the No. 1 wheel terminal on the side of the 4-pin plug cord on the side of the dry bunch.

Brown blue wire) and terminal 3 (blue wire).

Professional experience and special equipment, as well as a certain amount of work experience, only with these, can detect the resistance value of the temperature disturbance buried sensor and the slow imitation size of the power supply voltage, without these necessary conditions can not be detected, but also will not see.

Summary. Dear, hello, the solution to the failure of the car engine temperature sensor is as follows:1

High resistance fault The high resistance state of the water temperature sensor provides the cold engine status information to the engine ECU at any time, and the engine ECU sends out a low temperature fuel supply signal, which will continuously increase the fuel supply. The sensor expert network believes that when starting, because the water temperature signal obtained by the ECU is a cold car signal, the amount of fuel injection is increased to facilitate starting, and the spark plug is often soaked with fuel, and the engine is difficult to start, especially when the engine is warm. After starting, it has been supplied with a thick mixture, and the idle speed is high due to the rich oil.

What is the cause of the failure of the temperature sensor?

Dear, hello, the solution to the failure of the car engine temperature sensor is as follows:1High resistance fault The high resistance state of the water temperature sensor provides the cold engine status information to the engine ECU at any time, and the engine ECU sends out a low-temperature fuel supply signal, which will continuously increase the fuel supply.

The sensor expert network believes that when starting, because the water temperature signal obtained by the ECU is a cold car signal slippery number, so increase the amount of fuel injection to facilitate starting, the spark plug is often soaked with fuel, and the engine is difficult to start, especially when the engine is warm. After starting, it has been supplied with a thick mixture, and the idle speed is high due to the rich oil.

What are the symptoms and causes of temperature sensor failures?

1. When the temperature of the measured medium rises or decreases, the output of the transmitter does not change, and most of the cases are the problem of sealing the temperature sensor, which may be due to the fact that the temperature sensor is not sealed well or the sensor is accidentally welded with a small hole when renting and welding, which generally needs to replace the sensor shell to solve. Clause.

Second, the output signal is unstable, the reason is the temperature source ability, the temperature source ability is an unstable temperature, if the instrument display is unstable, that is the reason why the anti-interference ability of the instrument is not strong.

How to solve it? 1. When the temperature of the measured object rises or decreases, the output of the transmitter remains unchanged. Most of this is due to a sealing problem with the temperature family sensor, which may be due to the temperature sensor not being properly sealed, or the sensor accidentally soldering a small hole during the belt re-soldering process.

This situation usually needs to be solved by replacing the sensor housing.