The knock sensor is a critical component in the running of your vehicle. It is responsible for detecting engine detonation or knocking. It is critical to the effective operation of your car since detonation can ruin the engine.
As such, we recommend you check your knock sensor periodically to ensure it’s working correctly. If your having an issue with your knock sensor and need to test it or do routine maintenance we have you covered. In this post, we learn how to check the knock sensor with a multimeter.
To test the knock sensor, follow the below steps.
Locate the knock sensor of your vehicle on the engine manifold. Disconnect the wire harness from the knock sensor by pulling on the harness base at the point it meets the sensor. Take your multimeter and clip its lead to the knock sensor. Touch the multimeter’s negative lead to a ground point – like the negative battery terminal. If your knock sensor is in good shape, you should see continuity. Your multimeter should read 10 ohms and above.
What is Detonation?
It is a situation where the fuel in your car and air mixture explodes quickly instead of burning evenly. If your knock sensor is not working correctly, it cannot detect engine detonation. A properly working knock sensor usually has continuity – the presence of a current electrical path between the wire and the sensor. In the absence of continuity, the knock sensor cannot perform optimally. Thankfully, you can test if there is continuity in your knock sensor using a multimeter.
Do You Suspect a Bad Knock Sensor?
A couple of things happen when you have a bad knock sensor. Some tell-tale signs include low power, no acceleration, a popping sound after a check, and lost fuel mileage. Be on the lookout for sounds from the engine – loud thumping noises that seem to become worse over time. If you hear these noises, the possible culprit is the fuel and air igniting in the cylinder instead of getting to the point of combustion. (1)
Diagnosing a Bad Knock Sensor
You may perform a bad knock sensor diagnostic test in a couple of ways. For instance, if the check engine light is on is a sign of problems with the knock sensor circuit. As mentioned earlier, poor engine performance could potentially point to a bad knock sensor. Checking the Diagnostic Trouble Codes (DTCs) can help you find any existing issues that require immediate attention. A visual inspection would also do, and lastly, a direct test on the knock sensor using a multimeter.
How to Test a Knock Sensor with Multimeter
Below is a step by step guide on how to check the knock sensor with a multimeter:
- Park your car on level ground, engage the emergency brake and turn off the engine. Upon opening the hood of the car, turn the engine on. Opening the hood with the engine turned off helps to prevent possible injuries.
- Locate the knock sensor of your vehicle on the engine manifold. It’s usually mounted in the middle of the engine under the intake manifold. To avoid unnecessary issues as far as locating the knock sensor is concerned, consult your repair manual. The detailed diagram of the engine will come in handy. (2)
- Can you spot the wire harness? Disconnect it from the knock sensor by pulling on the harness base at the point it meets the sensor.
- Take your multimeter and clip its lead to the knock sensor. Touch the multimeter’s negative lead to a ground point – like the negative battery terminal. If your knock sensor is in good shape, you should see continuity. Your multimeter should read 10 ohms and above.
What if There is No Continuity?
A knock sensor multimeter test result that shows no continuity means that you should replace the sensor.
A knock sensor that is not working could lead to a pinging engine. The worst part is that the computer could fail to detect the pinging. To ensure optimal function of the engine, consider replacing a bad knock sensor.
Take a look at some of our related articles below.
- How to test 3-wire crank sensor with multimeter
- How to test 02 sensor with multimeter
- How to test a car ground wire with a multimeter
(1) combustion – https://www.britannica.com/science/combustion
(2) diagram – https://www.edrawsoft.com/types-diagram.html