Compromised diagnosis: how to detect which sensor is failing

Niterra explains how a defect in a single sensor can compromise engine performance and lead to erroneous diagnoses

São Paulo, outubro de 2025 – In modern vehicles, the sensors work together to ensure the engine works properly. That is why, a failure in just one of them can generate a chain reaction, affecting other systems and confusing the diagnosis. According to NTK, Niterra's brand, Japanese multinational also responsible for NGK, It is common for defects in sensors such as temperature (CTS), rotation, MAP or TPS cause similar symptoms, what does it take, often, incorrect replacement of components.

“The sensors constantly exchange information with the injection module. When one of them sends a wrong reading, the system incorrectly interprets and adjusts injection and ignition parameters, causing failures, at other points of the engine”, explains Hiromori Mori, Niterra Technical Assistance Consultant.

To assist in a more accurate diagnosis and support the routine of professional mechanics, NTK details the effects of failures on each sensor, as well as providing guidance on how to correctly identify them, helping to avoid unnecessary replacements and ensure good engine performance.

1. When the temperature sensor fails: the coolant temperature sensor (CTS) tells the electronic module whether the engine is cold or hot, through the direct correlation between the liquid temperature and the engine temperature. When it is defective, may indicate an incorrect temperature, for example, show that the engine is still cold even after warming up.

The system, So, injects more fuel than necessary, increasing consumption, impairing performance and making it difficult to start with a hot engine. This excess can affect the spark plugs, the catalyst and even the oxygen sensor (lambda probe), creating a sequence of failures that are difficult to identify.

2. Effects of faults on rotation sensors, Speed & MAP: Problems with these sensors can cause inconsistent readings for the injection module. As a consequence, the engine loses power, It has difficulty starting and the injection light on the dashboard may come on. O sensor MAP (absolute pressure), for example, plays a direct role in controlling the air-fuel mixture, where an incorrect reading interferes with determining the mass of air entering the engine, preventing the correct adjustment of the air/fuel mixture and making it difficult to burn correctly, reducing engine efficiency.

The rotation sensor, Indicates engine speed and position of the first cylinder (TDC – top dead center). Sensor failure can prevent the engine from running or cause longer starts when the engine has a valve control position sensor (phase sensor).

3- When the TPS sensor fails: The TPS sensor monitors the position of the throttle valve, informing the injection module how much the “driver is accelerating”, applied to systems that have accelerator cables. When it is defective, may cause failure during acceleration, loss of power or rough idling, These faults affect consumption and overall engine performance.

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Preventive maintenance makes a difference

Use the correct additive in the cooling system, Maintaining the cleanliness of the circuit and periodically checking the connectors and wires are precautions that preserve the accuracy of measurements and prevent corrosion. These simple measures help extend the life of the sensors and the engine itself., avoiding cascading failures.

“Sensors generate various information that is essential for the correct functioning of the vehicle’s various electronic systems.. Qualquer falha em um deles altera o seu funcionamento e até mesmo desabilitam partes dos sistemas eletrônicos. Technical knowledge and attention to detail are essential for a correct diagnosis”, highlights Mori.

Even essential for the operation of the vehicle, It is important to highlight that the defect is not always in the component. Oxidation, poor contact or contamination, Faulty electrical harnesses and sensor power problems can generate faults or reading errors, making it difficult to correctly diagnose the system. Before replacing a sensor, The ideal is to check the entire electrical circuit and compare the readings with the original factory parameters.

With this kind of guidance, Niterra reinforces its commitment to supporting automotive repair professionals, promoting technical knowledge and security for the sector. In addition to providing the market with a wide range of products developed with the highest technology and quality,, offers technical support to repairers with easy access through its SAC.

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