What is the measurement method for the two wires of a knock sensor?
3 Answers
The measurement method for the two wires of a knock sensor is: 1. Connect the computer diagnostic tool to the vehicle's computer fault diagnosis socket; 2. Start the car engine and set the computer diagnostic tool to data transmission mode; 3. Use a tool to tap the cylinder block near the two-wire knock sensor while observing the changes in the ignition advance angle value on the display screen. The functions of the knock sensor are: 1. To measure engine vibration and adjust the ignition advance angle when engine knock occurs; 2. It is an AC signal generator that detects the speed and position of the rotating shaft. The knock sensor includes: a magnetic core, permanent magnet, and induction coil.
I've tested those two wires of the knock sensor several times myself, and the method isn't difficult. The key is using a multimeter. First, locate the sensor position - usually there's a connector with two wires, one for signal and one for ground. Always turn off the engine and remove the key for safety first, never work on live circuits. Set the multimeter to resistance mode and measure between the two wires: if it reads zero ohms, there might be a short circuit; infinite resistance indicates an open circuit, meaning the sensor needs replacement. Normal values typically range in the thousands of ohms, depending on the specific vehicle model. After starting the engine, you can also measure voltage fluctuations - noticeable voltage changes occur during knocking. Sometimes aged wiring or loose contacts can cause issues too; I once encountered this and regained significant engine power after repair. Always check wire harness connections before and after measurements to prevent misdiagnosis and save money. A non-functioning knock sensor can damage the engine, so accurate testing prevents major overhauls. Beginners can attempt this job but must be careful and avoid improper tool connections.
I still remember the last time I fixed a customer's knock sensor issue, where the engine was noisy and fuel consumption was high. Before measuring the two wires, I first visually inspected the wiring harness for wear. After disconnecting the plug, I set the multimeter to ohmmeter mode to measure resistance—standard values should be checked in the manual, for example, some cars have a normal range of 2-5k ohms. If the resistance is normal, start the car and monitor the signal voltage; fluctuations during knocking indicate the sensor is good. I always remind not to rush—ensure the tool grounding is stable, or it might damage the wiring. Experience tells me most problems arise from poor wiring contact or sensor aging. Timely and accurate testing and part replacement can extend engine life. The entire process emphasizes safety precautions to prevent accidents, and measurement data should be compared against standards to avoid misdiagnosis and wasted money.
