2 wire water temp gauge sensor

• 2023-08-25

A 2 wire water temp sensor with a common ground wire and two signal wires: a water temperature gauge (5V) and a 12V supply to the engine computer. Install them in almost the same location. If the data output from two sensors differs significantly, it is determined that there is a problem with one of them. At this time, the throttle control is not determined based on the information from the sensors. The water temperature sensor has no structural changes, but its function is to provide an analog signal of temperature changes to the engine control unit. Its power supply voltage is provided by the control unit with a 5V power supply, and the signal returned to the control unit is a linear variation signal of 1.3V-3.8V.

The detection method of 2 wire water temp sensor: 1. Use a digital resistance simulator to simulate the water temperature and compare it with the actual situation; 2. Use an infrared thermometer to test the actual temperature of the water temperature sensor and compare it with the water temperature gauge; 3. Test the resistance value of the water temperature sensor with a multimeter, and heat the water temperature sensor with a hair dryer to reduce the resistance value; The car water temperature sensor is a thermistor, ranging from a few thousand ohms to several tens of thousands of ohms. The cause of the fault is a short circuit, open circuit, and poor contact. After measuring with a multimeter, it is basically clear that the most common fault is poor contact, followed by an open circuit, and the possibility of a short circuit is very low.

After the engine was stopped and the spark plug was removed, it was found that there was a large amount of carbon deposits on the electrodes, and the electrode gap was also large. Through routine inspection, it was confirmed that the fault was caused by excessive mixture concentration and misfire. Then short circuit the two sockets of the diagnostic terminal with the connecting wire, turn on the ignition switch, observe the number of flashes of the fault indicator light on the dashboard, and obtain a fault code of 14. After investigation, the meaning of this code is that the output voltage of the water temperature sensor is too low. Disconnect the water temperature sensor connector and use a multimeter to measure its resistance value as ∞, proving that the water temperature sensor has failed.