Coolant temperature sensor (DTOZH) Priora: replacement, where it is located, photos, faults

03 March 2017 Lada.Online 82 437 6

The coolant temperature sensor (CTS) is one of the elements of the engine management system. Its purpose is to control the temperature of the fluid in the cooling system. Based on these data, the engine control unit adjusts the composition of the fuel-air mixture, crankshaft speed, and ignition timing.

On all modern LADA cars (XRAY, Vesta, Largus, Granta, Kalina, Priora or Niva 4x4), replacing and checking the coolant temperature sensor is carried out in the same way.

DTOZH design and principle of operation

This sensor has a simple design without any complex electronic elements. A thermistor acts as an actuator.

It is the thermistor that regulates the quality and quantity of the fuel mixture during engine starting. That is, when starting in the cold season, the engine needs more fuel; this is built into the electronic engine control unit (ECU). Based on the DTO readings, the ECU passes the required amount of fuel through the injectors for normal engine operation in low temperature conditions.

The operation of the sensor can be noticed by increased engine speeds after start-up, which return to normal as they warm up to operating temperature. The thermistor is sharpened into a metal sensor housing with a thread and has two terminals for the ECU connector.

Also, based on the DTO readings, the ECU adjusts the ignition timing (IAF). The sensor receives power via one of the marks from the ECU with a voltage of 5V, while the second mark is connected to ground.

Since the sensor is in direct contact with the coolant, it estimates the engine temperature directly from the coolant temperature.

Signs of breakdown

Like any other part of the mechanism, the DTOZH in Priora periodically becomes unusable. It happens that the cause may be a broken indicator on the device, problems with the wiring, or a malfunction of the sensor itself. The following symptoms may indicate a malfunction:

continuous operation of the fan, which is designed to cool the engine - in this case, the machine will operate in emergency mode, and a constantly running mechanism will lead to burnout of the winding in the motor, which in the future will require a complete replacement of the unit;
the cooling fan does not turn on - in this case, increasing overheating of the engine will lead to boiling.

There are also indirect signs that may suggest a problem with the detector:

reduction in vehicle power;
presence of hum from constant operation of fans;
increase in consumption;
The engine often stalls and is difficult to start.

Symptoms of malfunction

The sensor exhibits the following malfunction symptoms:

The car's dynamics disappeared;
The temperature readings are no longer displayed on the dashboard;
The car is idling unsteadily;
Jerks appeared when driving at constant speeds;
There are no increased speeds when starting the engine;
The cooling fan does not work;

Based on these signs, it can be assumed that the DTOZH is out of order or is giving incorrect readings.

Checking the coolant temperature sensor on the Priora

The device we are considering, from the engine control system via a computer, when it fails, gives a signal and the “Check Anger” light on the dashboard lights up. The on-board computer always has an emergency built-in specialized program, and even if the coolant temperature sensor fails for some reason, the electronic unit will forcefully start the radiator fan. One clarification: in this case, the fan will work constantly. Pay attention to the main signs of a failure in the LADA Priora cooling system:

The panel displays a high temperature of the power plant.
The fan runs non-stop.
The "Check" light is on.

Be attentive to your car, and when the signal lights up on the dashboard, urgently undergo computer diagnostics of the electronic control unit. Thanks to such diagnostics, it will certainly be possible to identify the cause of incorrect operation.

Checking the DTOZH

The temperature sensor is the simplest device, so the principle of checking it is also quite simple.

To check the sensor you will need a multimeter and a thermometer.

The sensor must be checked by measuring the resistance on it as a result of measuring the temperature of the liquid. DTOZH increases its resistance as the liquid temperature decreases.

In order to check it, you need to connect a multimeter set to resistance readings to the ends of the sensor and lower it into a glass of boiling water. The ohmmeter reading should match the temperature reading. That is, using the table, we look for the water temperature and what resistance the sensor should have at that temperature.

Next, we perform the same procedure with cold water and look at the ohmmeter readings. Based on the measurements, we issue a verdict on the sensor.

Below is a table of DTOZH resistance depending on the coolant temperature.

Table of sensor resistance depending on temperature.

How to check

After removing the sensor, it should be visually inspected for damage or corrosion. The easiest way to check the DTOZH is to replace it with a known good one.

Required:

multimeter (in voltmeter mode, ohmmeter with a measurement limit from 100 Ohm to 10 kOhm);
thermometer (with a measurement limit of at least 100 °C);
heat-resistant container with a volume of 0.5 l.

The procedure for checking the power supply circuit of the DTOZH:

Switch the multimeter to voltmeter mode;
Remove the block with wires from the sensor and turn on the ignition;
Connect the negative probe of the multimeter to the engine ground, and the other to terminal No. 1 of the block;
The voltage at the output must be at least 12 V.

If there is no voltage or they are less than 12 V, it means that the battery is discharged, the power circuit or the computer is faulty.

Procedure for checking DTOZH:

Switch the multimeter to ohmmeter mode;
Prepare a container with hot water (about 100 oC);
Connect the multimeter probes to the sensor terminals and lower its working part into water;
We measure the resistance of the DTOZH as the water cools.

The sensor resistance should be close to the data shown in the table:

Coolant temperature, °C	DTOZh resistance, Ohm
100	177
90	241
80	332
70	467
60	667
50	973
45	1188
40	1459
35	1802
30	2238
25	2796
20	3520
15	4450
10	5670
5	7280
0	9420

The verification process is also shown in the video:

If the DTOZH turns out to be in good order, the cause of the malfunction may be poor connector contact, broken wiring, or a faulty ECU.

Do not forget to change the antifreeze/antifreeze in the cooling system on time, and use the coolant recommended by the manufacturer.

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Replacing the sensor yourself

Replacement is not a complicated process, but it has its own characteristics that must be observed when working.

Necessary tool

Key to "19"
Ratchet
Head at "13"
Screwdriver “+” or “-”

Replacement with coolant drain

Attention :
The coolant temperature sensor must be replaced with a cold engine.

Remove the negative terminal from the battery. In order to protect yourself and the car from a short circuit.

Remove the mass air flow sensor (MAF) chip.

Unscrewing the clamps on the intake receiver corrugation, remove the air filter housing along with the mass air flow sensor.

We remove the DTOZH chip.

Next, you need to drain the coolant.

Using a 13 key, unscrew the coolant drain plug in the cylinder block and drain the coolant into a 10 liter container.

Using a key set to “19”, unscrew the DTOZH from the thermostat housing.

We install a new DTOZH.

We assemble everything in reverse order.

After filling the coolant, do not forget to check its level.

Replacement without draining coolant

To replace the coolant sensor without draining the coolant, you must prepare a new sensor to quickly replace it.

We approach the DTOZH and begin to unscrew it, having previously prepared a new sensor and placing a cloth under the thermostat so as not to fill the gearbox with antifreeze.

We unscrew the sensor and sharply remove it, and plug the hole in the thermostat with a finger.

Next, we take a new sensor and also try to insert it into the hole in the thermostat as quickly as possible and screw the new sensor into place.

Then we assemble everything in reverse order.

Don't forget to check the coolant level and add it if necessary.

The DTOZH has been replaced as you can see, there is nothing complicated about it.

How the cooling system works on Priora

The system we are considering in the popular Lada Priora works by circulating fluid, as expected, through the radiator. The temperature decreases solely due to airflow. What types of blowing are there:

The look is natural. As the name implies, in this case the natural air flow cools the radiator while driving.
Kind of forced. When excessive heating occurs, the built-in fan is activated.

How does a fan work in the cooling system of a modern car:

Through the positive contact, current flows to the so-called winding of the installed fan.
The contact marked “-” is directed to the relay, which in turn is controlled by the ECU.
The ECU, based on a signal from the coolant temperature sensor, turns on a device such as a relay to ground.

Attention! The domestically produced car Lada Priora does not have 1 coolant temperature sensor, there are 2 of them. And these are completely different devices. The 1st sensor sends a signal to the main computer, the 2nd sensor is responsible for the movement of the arrow on the dashboard.

Cars with ECU: features

In ordinary modern carburetor cars, the operating temperature is lower than in “injection” cars. For the latter it is 102-105 degrees. It is known that with such heating, the most ordinary water will naturally begin to boil. Therefore, you only need to use antifreeze or, as an option, antifreeze, the boiling point of which is at around 115 degrees.

Lada Vesta galvanized body or not
Vesta fuel consumption
MMS Lada Vesta

The principle of operation of the DTOZH on Priora: how the fan switching device functions

The design of the element in question is based on a semiconductor element - a thermistor. When the temperature applied to the thermistor changes, the resistance increases or decreases. Below is a cross-section of the design of the temperature sensor, which will help you understand the principle of its operation.

Such an element is connected to the circuit using two contacts. Changes in temperature change the resistance, and as a result, the voltage in the circuit increases or decreases. The ECU records changes in voltage (drop), and depending on its value, makes appropriate decisions about preparing the mixture and adjusting the ignition. A voltage of up to 5V is supplied to the sensor from the controller through a 2 kOhm resistor, and depending on its fluctuations (drops), the electronic unit determines the engine temperature at the corresponding moment in time.

Location and serviceability check

This device is located directly above the Priora flywheel housing. The sensor is embedded in the engine block near the thermostat. It is connected to a single wire with a female connector. The test method for this device is very simple. And it has been used by drivers for a very long time. You need to do this:

Turn on the ignition.
Disconnect the connector from the sensor.
Connect the wire to the block body.

If the DTOZH itself is faulty, the indicator arrow will rise to its highest position. But if no changes occur on the instrument panel, then the reason must be looked for elsewhere. Maybe the circuit is broken, the pointer is broken, or the whole combination.

How to check

There are two options for checking the functionality of the sensor:

With the need to remove;
With thermometer;
Without thermometer;
Right on the spot, without taking off.

But first you need to make sure that the sensor is receiving power. Remove the chip from the DTOZH and measure the DC voltage with a multimeter. It should be about 5 V. If it is approximately within these limits, we check further.

Without removing the sensor, you can check its performance in the following way. We disconnect the chip. We measure the resistance between the sensor contacts. When the engine is cold, the resistance will be higher, and when the engine is hot, it will be lower. For example, let's give a data table for the VAZ-2110 car. For other cars that use similar sensors, the numbers will be approximately the same.

Recommendations for care and maintenance of sensors

Strictly adhere to vehicle maintenance schedules;
Buy parts with original catalog numbers. The exact data is indicated in the instruction manual for your technical device;
Carry out preventative maintenance, install consumables and spare parts at certified service stations. Relevant while the car is under factory warranty. There are frequent cases of warranty cancellation due to third-party intervention.
When the first signs of engine malfunction appear, contact a service station.

Where is the coolant sensor located on the Priora?

A device such as the ECU on the Russian LADA Priora needs up-to-date and reliable information about the temperature of the power unit. When choosing sensors in a store for their subsequent installation, this is what you should be guided by. The sensors are located at the so-called cooling “jacket”. The sensor that interacts with the computer is located in the metal thermostat housing, which in turn is installed on the head of the automobile cylinder block. Another sensor that interacts with the instrument panel is located in the cylinder block. Now you know where each coolant temperature sensor is located, you can easily find them if replacement is required.

Important! The sensor interacting with the dashboard has 1 contact, and the sensor working with the ECU has a 2-pin input.

In the photo below you can see both sensors in detail.

Operating principle

DTOZh "Priora" is installed directly in the thermostat housing. This allows for maximum pulse accuracy. Since DTOZH is always in contact with antifreeze, it can almost instantly detect the slightest changes in temperature. It also quickly transmits signals to the ECU. Based on the information received, the car’s brain adjusts the engine operating parameters, changing the composition of the fuel mixture.

If the antifreeze level is too low, the controller will receive incorrect data and the engine may run rough. This is also observed due to sensor failure.

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