Electronic car engine control system Nissan Almera Classic critically depends on the accuracy of temperature sensor readings. If the computer receives incorrect data about engine heating, this leads to incorrect operation of the ignition system, enrichment or leanness of the mixture, as well as problems with starting a cold engine. That is why knowing where physically is located coolant temperature sensor, is the first step in diagnosis.
Owners Nissan Almera Classic with the MR18DE series engine, they are often faced with the need to replace this element, since it is exposed to high temperatures and vibrations. A sensor malfunction can masquerade as problems with other systems, so it is important to be able to distinguish the symptoms and know exactly where the component is installed. In this article we will analyze in detail the design of the unit, the dismantling procedure and the criteria for choosing a new part.
Design and purpose of the temperature sensor
The coolant temperature sensor (CTS) is a thermoelectric device whose resistance changes depending on the heating of the antifreeze. IN Nissan Almera Classic this element plays a dual role: it transmits information to the instrument panel to display the temperature needle and, more importantly, sends data to engine control unit (ECU). Based on these data, the unit adjusts the ignition timing and the amount of fuel supplied.
If you notice that the arrow on the instrument panel behaves chaotically, and the engine is unstable at idle, the problem may be thermistor. Inside the sensor body there is a sensitive element, which over time can oxidize or lose its properties. This causes the ECU to βthinkβ that the engine is cold and constantly supplies a rich mixture, which causes increased fuel consumption and carbon deposits on the spark plugs.
It is important to understand that in the cooling system Nissan Almera Classic There may be two temperature sensors: one for display on the dashboard and the second, main one, for engine control. However, many modifications with the MR18DE engine use a single two-pin sensor, which performs both functions. Do not confuse this with the fan sensor, which is often built into the radiator or thermostat and has a different connector configuration.
The exact location of the sensor in the engine compartment
Find where it is coolant temperature sensor, on the MR18DE engine is quite simple if you know where to look. The element is installed on the body thermostat, which, in turn, is attached to the cylinder block. The thermostat is the assembly that connects the engine to the radiator pipes, so the sensor is immersed directly in the coolant flow.
For a visual inspection, you need to open the hood and find the upper radiator pipe coming from the engine. Run your fingers along it until you find the metal thermostat housing. The sensor is a small black plastic connector with two wires screwed into the top of this housing. It is located closer to front of the engine, on the radiator side, which makes it accessible for replacement without complex disassembly of the engine compartment.
Sometimes access to the sensor may be difficult due to additional protection or brackets installed. In this case, you may need to remove the plastic decorative engine cover, if your equipment includes one. note that electrical connector usually secured with a plastic latch, which must be carefully pressed so as not to break the latch.
Do not confuse the installation location of the sensor with the throttle valve heating pipe. Although both elements are located at the top of the engine, the DTOZH is always screwed into the thermostat βboxβ, and not into thin corrugated tubes. An erroneous attempt to locate the sensor in another location will result in wasted time and possible injury from hot engine parts.
Symptoms of malfunction and diagnostic methods
You can understand that the sensor has failed by several characteristic symptoms that manifest themselves in the behavior of the car. The most obvious sign is unstable engine idling, especially when warm. The ECU receives a false signal about a low temperature and tries to warm up the engine by increasing the speed, which leads to βfloatingβ tachometer readings.
Another warning sign is increased fuel consumption. If temperature sensor βstuckβ and indicates that the engine is always cold, the injection system will constantly supply a rich mixture. This can also result in difficulty starting a hot engine because the mixture becomes too oily to ignite properly. The temperature gauge on the dashboard may also be stuck down or show unrealistically high readings.
For accurate diagnosis, you must use a multimeter and a diagnostic scanner. The scanner will show the real temperature that the control unit βseesβ, comparing it with the readings of the atmospheric sensor. You can use a multimeter to check the resistance of the thermistor itself. The resistance value should change smoothly as the sensor heats up, and not jump chaotically.
- π΄ The engine stalls immediately after starting if the sensor shows the wrong temperature.
- π΄ The "Check Engine" icon on the dashboard lights up with temperature-related error codes.
- π΄ The cooling fan turns on too early or does not turn on at all.
β οΈ Attention! If you notice that the antifreeze is rust-colored or has a lot of deposits in it, this could be a sign of an overheating engine, caused not only by a faulty sensor, but also by problems with the cooling system as a whole.
- Unstable speed
- Engine overheating
- Increased fuel consumption
- Temperature needle doesn't move
Tools and preparation for replacement
Before starting work, it is necessary to prepare all the necessary tools so that the replacement process goes quickly and without unnecessary delays. You will need a standard set of wrenches, specifically a wrench 19 mm or a special key for sensors, since the sensor housing often sticks to the thermostat housing. You will also need a container to drain some of the coolant, since when the sensor is removed, antifreeze will inevitably leak out.
Be sure to check that a new sensor is available and that it matches the original number. On Nissan Almera Classic Sensors with a specific temperature range are used, and installing the wrong part may result in engine malfunction. Also have a new O-ring or copper washer ready, as the old washer may leak after reuse.
It is better to carry out work on a cooled engine. If you try to unscrew the sensor on a hot engine, there is a risk of serious burns from splashes of boiling water or steam under pressure. Let the car sit for at least 30-40 minutes after stopping. Open the expansion tank to release any remaining pressure in the system.
βοΈ Preparing to replace the sensor
Step-by-step instructions for dismantling and installation
The replacement process begins by disconnecting the battery. Disconnect the negative terminal to eliminate the risk of a short circuit when working with the electrical connector. Then find electrical connector on the sensor and gently press the latch to disconnect the wiring. Do not pull the wires, only pull the plastic part of the connector.
Use a wrench to unscrew the old sensor. Do this slowly as the threads may become stuck. If the sensor does not budge, you can use penetrating lubricant (WD-40), but be careful not to get it on the electrical contacts. After removing the sensor, immediately drain the leaked coolant into a prepared container.
Clean the threaded hole in the thermostat housing from dirt and old sealant. Install a new sealing washer on the new sensor if it is not installed at the factory. Screw in a new one temperature sensor by hand until snug, then tighten with a moderate torque wrench. Over-tightening may damage the plastic housing or strip threads.
Connect the electrical connector until you hear a characteristic click, making sure that the latch is engaged. Fill the system with coolant to the required level, removing any air pockets. Start the engine and check for leaks where the sensor is installed. Let the engine idle until the temperature gauge rises to normal.
β οΈ Attention! If the error on the dashboard does not disappear after replacing the sensor, the problem may lie in the wiring or the engine control unit itself, and not in the sensor.
| Parameter | Value for MR18DE |
|---|---|
| Original part number | 22613-ED00A (example) |
| Key size | 19 mm |
| Connector type | 2 pin |
| Housing material | Plastic with metal thread |
| Torque | 15-20 Nm |
What to do if the sensor is stuck?
If the sensor cannot be unscrewed, do not use excessive force to avoid breaking the thermostat housing. Use the heat of a hair dryer or blow dryer on the threads, as well as a penetrating lubricant. Give it time to work and try again with a little effort.
Choosing a high-quality analogue and original
When choosing a sensor for Nissan Almera Classic It is worth considering the balance between price and quality. Original parts from Nissan usually cost more, but guarantee accuracy and durability. However, there are many proven analogue manufacturers on the market that offer decent quality at a more affordable price.
Famous brands such as Denso, Pierburg or Calsonic, often supply parts to the assembly line and are an excellent alternative. When purchasing, be sure to check the integrity of the packaging and the presence of a quality certificate. Counterfeit sensors may have incorrect temperature characteristics, leading to ongoing engine problems.
Pay attention to the case material and the quality of the contacts. The plastic must be durable and heat-resistant, and the contacts must be covered with a protective layer against oxidation. If you buy a used part, it is extremely risky, since the wear of the thermoelement inside the housing cannot be checked without special equipment.
- β Always check the part number with your vehicle's catalog before purchasing.
- β Avoid purchasing sensors without packaging and manufacturerβs markings.
- β Make sure a new sealing washer is included.
The original sensor provides maximum accuracy, but high-quality analogues from trusted brands (Denso, Calsonic) can be an excellent replacement if selected correctly.
Nuances of operation and prevention
The durability of the temperature sensor depends not only on the quality of the part itself, but also on the condition of the entire cooling system. The use of low-quality antifreeze, which over time loses its properties and becomes aggressive, can lead to corrosion of the sensor housing and disruption of its operation. Regular replacement of coolant is the key to a long life of all sensors.
It is also important to keep the contacts in the connector clean. Moisture and road salt can cause oxidation, resulting in false readings. Periodically inspect the connector and clean it with coupling fluid if necessary. If you notice traces of corrosion on the wires, it is better to replace them or carefully insulate them.
When parking a car for a long time in the cold season, it is recommended to use a pre-heater if climatic conditions require it. This will reduce the load on the engine and cooling system at startup, which will indirectly extend the life of all temperature sensors. The correct choice of antifreeze and regular diagnostics of the cooling system are the key to uninterrupted operation of the temperature sensor.
β οΈ Attention! Never mix antifreeze of different colors or brands, as the chemical reaction can cause a sludge to form that will clog the passages and damage the sensor.
How to check a temperature sensor with a multimeter?
To check, you need to disconnect the sensor connector and measure the resistance between the contacts. At room temperature (about 20Β°C) the resistance is usually 2-3 kOhm. Heat the sensor in water and watch the resistance change - it should gradually decrease as it heats up. If the readings do not change or fluctuate, the sensor is faulty.
Is it possible to drive with a faulty temperature sensor?
Technically possible, but not recommended. The engine will operate in a non-optimal mode, which will lead to increased fuel consumption, accelerated wear of the cylinder-piston group and possible overheating if the fan does not turn on in time.
How long does it take to replace a sensor?
If you have the necessary tools and there is no sticking of the sensor, replacement takes about 30-40 minutes, including draining and filling with antifreeze.
Why does the temperature needle drop to zero when driving?
This may be a sign of an open circuit in the sensor or failure of the thermistor itself. The problem may also be in the wiring, which breaks due to vibrations.
Before purchasing a new sensor, take a photo of the old sensor and its connector with your phone to make sure you are buying a part with the same design and pin layout.