How to Test a Two-Wire Knock Sensor?
2 Answers
Testing method for a two-wire knock sensor: 1. Connect the computer diagnostic tool to the vehicle's OBD-II port; 2. Start the engine and set the diagnostic tool to data stream mode; 3. Use a tool to tap the engine block near the two-wire knock sensor while observing changes in the ignition timing advance angle displayed on the screen. The knock sensor is installed at various locations on the engine block or cylinder, and its function is to measure engine vibration. When engine knocking occurs, it adjusts the ignition timing advance. The knock sensor also acts as an AC signal generator, capable of detecting the speed and position of rotating shafts like magnetic crankshaft and camshaft position sensors.
I usually enjoy tinkering with my car, and there's a down-to-earth method to test a two-wire knock sensor: First, disconnect the sensor plug and measure the resistance with a multimeter. Normally, it should have a specific resistance value—if it shows infinity or zero, it's faulty. Then, you can start the engine for testing. Have an assistant rev the engine to around 2000 RPM while you measure the voltage changes with the multimeter. Normally, the voltage should fluctuate as the RPM increases. If there's no response, the sensor is likely dead. It's best to test when the engine is warm, as cold engine readings aren't accurate. Finally, don’t forget to check the wiring for any wear or exposed insulation—many faults are actually wiring issues. The whole process takes about ten minutes, but be careful not to short the multimeter probes on the terminals.
