Know your sensor: exhaust gas temperature sensor

Due to continuous strict emission regulations, the exhaust temperature sensor is becoming more and more popular in modern vehicles. And because they are parts with high failure rates, they are becoming more and more popular. Here, we will explain the role, the cause and method of failure, and how to replace it, so that you can use this rapidly growing service opportunity to provide high -quality and best maintenance services.

What is an exhaust gas temperature sensor?
As the name suggests, the temperature sensor of the exhaust gas measures the temperature of the exhaust gas. The information was then reposted back to the engine control unit or ECU, where appropriate action was taken. In gasoline engines, the main role is to protect key components from the impact of higher temperatures commonly from small engines -therefore, if the sensor detects too much temperature, the ECU will reduce the temperature by reducing the pressure pressure pressure of the turbocharger to reduce the temperature For example, or increase the amount of fuel sprayed by the catalytic converter. In the diesel engine, the exhaust gas temperature sensor is also used to monitor the temperature of the diesel particle filter (DPF) to establish the correct regeneration temperature, thereby reducing harmful emissions. It is not uncommon to install three or more sensors on the exhaust device; one before the turbocharger

How does the exhaust gas temperature sensor work?
There are two types of exhaust gas temperature sensors; one with a positive temperature coefficient (PTC) sensor element, and the other with negative temperature coefficient (NTC). The only difference is that they measure the temperature. NTC components have high resistance at low temperatures and low resistance at high temperatures. In other words, its resistance decreases as the temperature rises. In the most common PTC components, resistance increases with temperature. Whenever the method, the resistance allocation temperature in the ECU will be taken and corresponding measures.

Why does the exhaust gas temperature sensor fail?
One of the common causes of the exhaust temperature sensor failure is exposed to excessive temperature -in some cases exceeding 900 ° C -they protect other components from high temperature effects. Like all wired sensors, the violent vibration will also loosen the internal connection, and any bending or twist will cause the wire to break, causing them to be particularly easily damaged when changing other components in the exhaust system. These, as well as pollution from other fluids (such as oil or antifreeze), can affect the response characteristics of the sensor, leading to its drift exceeding the tolerance and providing inaccurate readings.

What are the symptoms of exhaust gas temperature sensor failure?
The faulty exhaust temperature sensor will have a negative impact on the post -processing system of the vehicle, leading to the following symptoms:

● Check the engine lights: If the ECU detects the sensor or signal problem, it will trigger the check of the engine light.
● Decrease fuel efficiency: If the voltage transmitted by the sensor is incorrect, the DPF regeneration process may take longer, resulting in increased fuel usage.
● Unnecessary DPF regeneration: Sensor failure can also lead to unnecessary regeneration, bringing inconvenience to the owner.
● Failure to discharge testing: The wrong reading will cause the EGR system to fail without triggering to check the engine light. This may lead to the failure of the emission test.
● Component failure: The increased exhaust temperature will also cause premature failure of other exhaust or internal engine components.

How to exclude the failure of the exhaust gas temperature sensor?
To diagnose a faulty exhaust temperature sensor, consider the following steps:

● Perform electronic testing and use diagnostic tools to read any fault code.
● Check the signs of corrosion or connection of the connector.
● Check whether there may be a break or damage to the short circuit of ground.
● Check whether the sensor has pollutant accumulation and clean it with clean dry cloth as needed.
● To test the sensor, use a separate IR measurement device, and compare the readings with the real -time data obtained when using the diagnostic tool. Run the engine to increase the exhaust temperature and compare the readings.
● Open the vehicle ignition switch and disconnect the plug on the EGT sensor to measure the voltage on the sensor connector -should be 5 volts. If not, trace the wires back to the ECU and check the power there.

What are the common exhaust gas temperature sensor failure code?
Common fault code includes:

● P0544: exhaust temperature sensor, group 1, sensor 1 -circuit failure
● P0546: exhaust temperature sensor, group 1, sensor 1 -high input
● P2033: exhaust gas temperature group 1, sensor 2 -circuit voltage high
● P247A: exhaust temperature sensor group 1, sensor 3 -beyond range
● P0549: exhaust temperature sensor, group 2, sensor 1 -circuit voltage high
● P2031: exhaust gas temperature group 1, sensor 2 -circuit failure
Please note that according to the design, the PTC sensor will continue to pass the error message to the ECU without setting the diagnostic failure code.

How to replace the exhaust gas temperature sensor?
If there is a problem with the temperature of the exhaust gas, you need to replace it -just follow the best practice suggestions:

● Positioning fault sensor. Please note that the location may be different according to its functions; turbochargers, catalytic converters and DPF upstream or downstream and NOX restore systems.
● Next, disconnect the electrical connector and use the sleeve wrench to unscrew the sensor. Be careful not to damage the nearby components.
● Prepare new sensors, apply the cardproofing agent on the thread if necessary. Be careful to prevent damage to the component.
● Install a new exhaust gas temperature sensor and tighten the torque in accordance with the advice of the vehicle manufacturer.
● Re -install the electrical connector, and then the battery negatives.
● Re -connect the diagnostic tool and delete all related fault code.
● Turn on the ignition switch and confirm that the engine light is off and the exhaust system works normally.
● Finally, take a road test.