Everything to know about your knock sensor

You're cruising down the highway in the hot sun, not a care in the world… when you hear it. A strange, rhythmic knocking, like someone tapping on the engine block with a tiny hammer. It sounds like trouble; the expensive kind. That’s where an engine knock sensor comes in— it potentially reduces risk of engine damage in this kind of situation.

So let’s take a look at the world of knock sensors, exploring what they do, signs that they’ve stopped working, and how to test and replace them.

What is a knock sensor?

There are many things that could go wrong with a car engine, and luckily there’s plenty of intelligent sensors in modern cars to take out the guesswork—like knock sensors. These nifty gadgets keep tabs on vibrations and sound levels in your engine, communicating with your car's computer so it can adjust the timing and help you avoid needing major repairs further down the road.

What does a knock sensor do?

So how does a knock sensor work? Well this small device “listens” out for suspicious knocking sounds coming from your engine. Engine knock can happen when the air-fuel mixture ignites prematurely in the combustion chamber, causing a mini-explosion that can wreak havoc on your engine's internal components.

The knock sensor function is to detect these vibrations and relay this information to the engine control unit (ECU) in your car’s computer, which adjusts the ignition timing as needed to prevent damage to the engine.

Knock sensor location: where is it?

Because its job is to listen to the engine, it makes sense that the knock sensor would be located close by. The most common position you’ll find a knock sensor is on the left side of the engine block, just below the intake manifold. However, in some vehicles, it can also be found on the cylinder head or intake manifold.

Knock sensor symptoms that mean it could be faulty

So what happens when a knock sensor goes bad? Here are some common symptoms of a bad knock sensor:

If you notice any of these things then you might have knock sensor problems, so it’s best to get it checked out by your local mycar mechanic.

Can a bad knock sensor cause rough idle?

Yes, a faulty knock sensor can cause rough idle. This is because the sensor plays an important role in regulating the engine's timing, which can affect how smoothly it runs at idle. So if your car is running rough then it’s a good idea to get the issue diagnosed and fixed quickly.

How to test knock sensor

Testing a knock sensor requires a bit of technical know-how and some specialised equipment. First up try these trouble-shooting tips:

Once you’ve checked these off it’s time to test the sensor itself. Here's a basic outline of the process.

Check the knock sensor circuit

Check the knock sensor operating performance

If all this sounds like a bit too much trouble, give us a call at your local mycar and our experts will have it tested without all the hassle.

How long can I drive with a bad knock sensor?

While you can technically drive with a faulty knock sensor, it's not recommended. Without this little gadget monitoring your engine, your car’s computer is in the dark about whether the timing needs adjusting. This means that you could end up damaging the catalytic converter, the pistons, valves, and more. So ignoring the issue could potentially end up costing you a lot more in the long run.

Can I repair a knock sensor myself?

It’s definitely possible to do a knock sensor replacement yourself, but we recommend only attempting this if you're experienced in automotive repairs and have the necessary tools. Improper installation can cause problems with the engine control system and potentially driving safety, so if you haven’t had a lot of mechanical repair experience then it’s best to leave it to the professionals.

What causes knock sensor failure?

Knock sensors can fail due to a variety of reasons, including incorrect installation, maintenance issues, internal short circuits, breaks in wiring, mechanical damage, incorrect mounting, and corrosion. Regular maintenance and proper installation can help prevent these issues, so make sure not to put off your yearly service.

Still not sure? Drop into mycar for help

If you're still unsure about your knock sensor or you need professional servicing, testing, or replacement, mycar is here to help. Our expert technicians can diagnose and repair any issues with your knock sensor, ensuring your engine runs smoothly and efficiently. With our workmanship guarantee, you can trust mycar to get you back on the road in no time!

Book a service or repair with mycar today.